The Progress of Invention in the Nineteenth Century Part 18

blood, is heated by the pa.s.sage of steam through it. The alb.u.men of the serum coagulates and rises to the surface in a sc.u.m which entangles the impurities and bone black, leaving the syrup light in color. The latter is then filtered through bone black until it is colorless and is then evaporated in the vacuum pan, which is the important invention of the century in sugar making. Heat has the effect of converting the crystallized sugar into the uncrystallized variety, and hence the evaporation must, to prevent this, be conducted at a low temperature.

Contact with the air is also objectionable. These conditions are provided for by conducting the evaporation in a vacuum, which lowers the evaporating temperature and avoids contact with the air. The vacuum pan was the invention of Howard, an Englishman. (British Pat. No. 3,754, of 1813). As constructed to-day it is an enormous vessel (see Fig. 173), capable of holding 7,000 or more gallons, and yielding 250 barrels of sugar at a strike. In this a vacuum is maintained by a condenser, the vapors pa.s.sing from the pan to the condenser through the great curved pipe rising from the top, which pipe is five feet in diameter. A gentle heat is applied through internal steam-heated coils which connect with an external series of steam inlet pipes on one side, and a corresponding series of steam outlet pipes on the other. A large discharge valve for the concentrated syrup closes the bottom of the pan. After concentration the crystallized sugar is separated from the syrup by a centrifugal filter, in which the liquid is thrown from the crystallized sugar by centrifugal action. The first centrifugal filter is shown in British patent to Joshua Bates, No. 6,068, of 1831. This, however, revolved about a horizontal axis. The present form of centrifugal filter is a cylinder revolving about a vertical axis, the sides of the cylinder being formed of filtering medium, through which the liquid is thrown by centrifugal action, while the sugar is retained within. This was the invention of Joseph Hurd, of Ma.s.s., U. S. Pat. No. 3,772, Oct. 3, 1844; re-issue No. 607, Sept. 29, 1858, which patent was extended for seven years, from Oct. 3, 1858. The diffusion process, which extracts the juice by cutting the cane in slices and soaking in water; the baga.s.se furnace, which dries and burns the expressed cane stalks as fuel, and the manufacture of glucose and grape sugar by the reaction of sulphuric acid on starch, are interesting allied features of this industry which can only be briefly mentioned. Most of the sugar consumed in the United States is imported, much raw sugar being imported and refined here. The imports for the year 1899 were 3,980,250,569 pounds, and the per capita consumption in 1898 was 61.1 pounds a year.

_Aids to Digestion._--It is only during the last part of the Nineteenth Century that the world has learned how to live. "What is one man's food is another man's poison" has been a trite old saying for many years, but the reason why has only in late years been fully understood. The physiology of digestion, the relative digestibility of different articles of food, and their nutritive values, have received of late years the earnest attention of physicians and students of dietetics and have contributed much to the quality and kind of food, and a knowledge of when and how to eat it. We know that the starchy foods are digested by the saliva, which is an alkaline digestion; that meat, fish, eggs, cheese and the alb.u.menoids are digested in the stomach by the gastric juices (pepsin and hydrochloric acid) which is an acid digestion, and that the remaining portions of starch, the sugars, and fats are digested in the intestines, and that this is also an alkaline digestion, and this has helped to solve the problem for us. We also know that starch is an excellent food, provided the vital powers are sufficiently stimulated by fresh air, sunlight, and exercise to digest it, as do the horse and the ox when they eat corn, but we know furthermore that the sedentary occupations of modern life leave many stomachs in a condition unable to a.s.similate starch, and so bread, oatmeal, potatoes and such simple staples, instead of nourishing the body, ferment in the enfeebled stomach, produce acids and gas, and lay the foundation for serious chronic diseases. The student of chemistry and dietetics knows to-day that one part of diastase will effect the conversion of 2,000 parts of starch into grape sugar, as a preliminary step to its digestion, and so by treating starchy matter with substances containing diastase (derived from malt) a partial transformation is effected which will materially shorten and a.s.sist its digestion. This fact has been largely made use of in the preparation of easily soluble or pre-digested foods, examples of which are found in patent to Horlick (malted milk), No. 278,967, June 5, 1883; to Carnrick (milk-wheat food), Dec. 27, 1887, No. 375,601; and Boynton and Van Patten (cereals and diastase), 344,717, June 29, 1886.

_Beverages._--Pure water, nature's own gift, has ever supplied every legitimate need of the human race, but civilized life has greatly extended its list of drinks, much to its own detriment. Soda water, whiskey, beer, ginger ale, tea, coffee, and chocolate represent enormous industries, and probably all do more harm than they do good. Much inventive genius in the Nineteenth Century has been bestowed upon the soda water fountain, on stills, and processes for aging liquors and processes for brewing beer, on cider and wine presses, on bottling machines and bottle stoppers, on devices for carbonating waters, and in coffee and teapots. The trend of the times is shown in the following figures, which represent the per capita consumption of beverages in the United States for 1898: tea, .91 of a pound; coffee, 11.45 pounds; wines, .28 of a gallon; distilled spirits, 1.10 gallons; and malt liquors 15.64 gallons. The largest per capita increase since 1870 has been in malt liquors, and the next in coffee. In tea and distilled spirits there has been a decrease, while the consumption of wines is the smallest of all and has varied but little.

CHAPTER XX.

MEDICINE, SURGERY, SANITATION.

DISCOVERY OF CIRCULATION OF THE BLOOD BY HARVEY--VACCINATION BY JENNER--USE OF ANaeSTHETICS THE GREAT STEP OF MEDICAL PROGRESS OF THE CENTURY--MATERIA MEDICA--INSTRUMENTS--SCHOOLS OF MEDICINE--DENTISTRY --ARTIFICIAL LIMBS--DIGESTION--BACTERIOLOGY, AND DISEASE GERMS-- ANTISEPTIC SURGERY--HOUSE SANITATION.

In the early gropings through the uncertain light of first progress, man was accustomed to ascribe the ills of his flesh to the anger of the G.o.ds, and in his craven and abject superst.i.tion made peace offerings.

Later he learned to locate the cause within himself, and constructed the theory that the fluids of the body had become disordered. The characteristic feature of progress in the Nineteenth Century, in this field, has been in the accurate tracing of the relation of cause and effect, and with the discovery of true causes has grown efficient means of treatment. The old expedients of charms, incantations, conjuration and exorcism gave place first to intelligent medication, and this in turn is rapidly giving way to the prevention of disease by improved conditions of sanitation and right living. The ounce of prevention has been found to be worth more than the pound of cure. With the improved knowledge of physiology, anatomy, chemistry and biology, which the century has brought, the intelligent physician was able to make a logical and for the most part a correct diagnosis, but supplemented with the microscope, that great revealer of the unseen world of small things, corporeal existence itself becomes an open book, and from the principles of organic evolution to the germ theory of disease the mystery of life and death is being slowly revealed.

When the Eighteenth Century gave birth to the Nineteenth, its great natal gift in medicine was vaccination. Jenner in 1798 for the first time announced his discovery of this great boon to the human race. In 1799 Dr. Benjamin Waterhouse, in Boston, obtained virus from Jenner and vaccinated four of his children, and in 1801 Dr. Valentine Seaman obtained virus from Dr. Waterhouse and performed the first vaccination in New York. During the Seventeenth and Eighteenth Centuries the annual death rate from smallpox in London ranged from 2 to 4 per 1,000 of population. In 1892 it was only 0.073 per 1,000.

It is also stated on good authority that the mortality from smallpox in England alone, was 20,000 a year less after the introduction of vaccination than it was in the preceding century, and that its benefits to the world at large have been so great that the lancet of Jenner has saved more lives than were sacrificed by the sword of Napoleon.

Each century in modern history has been marked by some important discovery in the field of medicine. The Seventeenth Century was notable for the discovery of the circulation of the blood by Harvey; the Eighteenth Century brought with it vaccination by Jenner. The Nineteenth Century's greatest gift in this field has been anaesthesia, or insensibility to pain. Nature has wisely endowed man with nerves of sensation as danger signals for the conservation of life. Accident and disease, however, are the inseparable concomitants of human existence, and suffering and pain the ineffaceable legacies of mortality. Sometimes these nerves of sensation are no longer useful as monitors, and in the unavoidable emergency of accident, surgical operations, child birth, and certain diseases, suffering can do no good, and then pain--that Prince of Terrors--thrusting his presence upon the hapless victim, racks body and limb, calling forth groans, and shrieks and writhings, till the poor sufferer, possessed with a dominating agony which displaces all thought of life, memory of friends, and love of G.o.d, breaks down in unutterable distress, and prays for death and oblivion. To this poor sufferer insensibility is next to heaven. For the past half century all the formidable operations of the surgeon have been performed with the aid of anaesthetics and without suffering to the patient, producing happy recoveries, and greatly contributing to the success of the result by relieving the surgeon of the distraction of the patient's pain, and the interference of his involuntary movements. Quite a number of anaesthetics are known and used to-day. Those more generally employed are--naming them in the order of their first application--nitrous oxide gas, ether, and chloroform. Nitrous oxide gas is chiefly used for the extraction of teeth. Sir Humphrey Davy, in 1800, was the first to observe the peculiar quality of nitrous oxide gas, which gave it the name of "laughing gas,"

from the fact that it caused those inhaling it to act in a manner exhibiting an abnormal exhilaration. Dr. Horace Wells, a dentist of Hartford, Conn., in 1844, had the gas administered, experimentally, to himself during the operation of extracting a tooth, and was the discoverer of its useful application as an anaesthetic.

The greatest discovery, however, in anaesthetics is the application of ether for this purpose. Ether as a chemical product has been known for several centuries, and as early as 1818 Faraday pointed out the similarity between the effects of ether and nitrous oxide gas. Dr.

Morton, a dentist, of Boston, first applied it as an anaesthetic Oct. 16, 1846, being guided largely in its selection and use by Dr. Jackson, an eminent chemist of the same city. On Nov. 12, 1846, U. S. Pat. No. 4,848 was issued to them for this invention. In the latter part of December of the same year Dr. Liston, an eminent English surgeon, performed the operation of amputating the thigh while the patient was under the influence of ether.

Chloroform, discovered by Guthrie in 1831, was first applied as an anaesthetic by Sir James Y. Simpson, of Edinburgh, in 1847. Of the two leading anaesthetics, ether is more generally used in the United Sates and chloroform in Europe. Ether is less dangerous, but its administration is more difficult and disagreeable. It is said on the highest authority that in the Crimean War chloroform was administered 25,000 times without a single death, and ether is even safer than chloroform. In the hands of a skillful physician practically no danger is to be apprehended from the use of either of the two agents. A little over fifty years ago any severe or prolonged surgical operation involved such irresistible pain that the patient's writhings were required to be restrained by powerful muscular a.s.sistants, and by straps which bound the patient to the table, and when it is remembered that a false cut of a hundredth part of an inch might be fatal, the haste, the disquieting influence upon the surgeon, and the interference with the accuracy of his hand, added greatly to the percentage of unsuccessful operations, as well as to the prolonged agony of the patient. Contrast this with the present methods of using anaesthetics, and we find the patient dropping into a quiet and peaceful sleep before the operation, and awakening thereafter to find, to his astonishment, that it is all over, and that recovery is only a question of careful nursing.

_Materia Medica._--Many important contributions have been made to the pharmacopia in the century. In 1807 the remedy known as ergot was brought to the notice of the profession by Dr. Stearns, and named by him pulvis parturiens. Iodine was first used as a medicine in 1819 by Dr.

Coindet, Sr., of Geneva. Quinine was discovered by Pelletier and Caventou in 1820, although Peruvian bark had long been used for the same purpose. Chloral hydrate, discovered by Liebig in 1832, was applied in medicine in 1869 by Dr. Liebreich, of Berlin. Carbolic acid was discovered in 1834 by Runge. Artificial seidlitz powders were first put up under Savory's British Pat. No. 3,954, of 1815. Veratrum viride, lobelia, worm seed, and chloroform were all introduced in the first part of the century. The sulphates of morphia, strychnia, atropia and other alkaloids are of comparatively recent addition to the pharmacopia, and the iodide of potash, tincture of iron, digitalis, bichloride of mercury, sub-nitrate of bis.m.u.th, boracic acid and gallic acid, chlorate of potash and Dover's powders have become standard remedies within a hundred years. In the latter part of the century the new remedies derived from coal tar have occupied an important place. Of these may be mentioned antipyrine, by Knorr (pat. Oct. 28, 1884), phenacetin, by Hinsberg (pat. March 26, 1889), salol, by Von Nencki (pat. Sept. 28, 1886), sulfonal, by Bauman (patented Jan. 22, 1889), antikamnia (acetanilide), and many others, besides new and valuable antiseptic compounds, such as salicylic acid and formalin. A characteristic feature of the modern practice of medicine is in improved forms of its administration. Sugar-coated pills, gelatine capsules and cod liver oil emulsions make the remedy much less disagreeable to take, and very ingenious and effective machines have been devised for putting up remedies in such forms.

[Ill.u.s.tration: FIG. 174.--THE OPHTHALMOMETER.]

_Instruments._--Laennec's discovery in 1819 of auscultation, and the stethoscope, for determining internal conditions by sound, was a great step in diagnosing diseases. The binaural stethoscope was invented by Cammann in 1854, and a later improvement is the phonendoscope, by Bianchi. The opthalmoscope is an instrument for inspecting the interior of the eye, which was invented by Prof. Helmholtz, and described by him in 1851. The laryngoscope, for obtaining a view of the larynx, was said to have been constructed by Mr. John Avery, of London, as early as 1846.

The opthalmometer, Fig. 174, is a comparatively recent invention. It is designed to ascertain variations in corneal curvature for the correction of corneal astigmatism. Electric lights with reflectors are arranged on each side of the patient's head, while the operator looks into the eye with a telescope. The sphygmograph, a little instrument to be strapped on to the wrist to record the action of the pulse, was first reduced to a practically useful form by Marey in 1860. A later development of these devices, by Verdin, known as the sphygmometrograph, is shown in Fig.

175. The endoscope, for looking into the urethra, and the cystoscope, for looking into the bladder, are other useful instruments of the modern pract.i.tioner. Greater than them all, however, is the modern X-ray apparatus, for locating foreign substances in the body and making visible the bones through the flesh, for which see special chapter. The use of the thermometer in recording the progress of fevers is also a valuable modern application, and the list of instruments and small tools is beyond enumeration. There are series of obstetrical appliances, instruments relating to bone surgery, to the taking up of arteries, cupping instruments, trepanning instruments, speculums, hypodermic syringes, electric cauteries, fracture appliances, instruments for lithotrity, bandages for varicose veins, atomizers, breast pumps, inhalers, nasal douches, trusses, pessaries, catheters, abdominal supporters, and an endless variety of proprietary articles, such as electric baths and belts, plasters, chest protectors, liver pads, and so forth, all of which are practically the products of the Nineteenth Century. The surgeon of to-day can straighten the eyes of a cross-eyed man, or take the bow out of his bandy legs, can make him a new nose of his own flesh, patch his skull with a silver plate, remove the stone from his bladder, supply him with a wind-pipe, wash out his stomach, and perform many other operations even more difficult. Among such more important operations may be mentioned ovariotomy, which was first performed by Dr. Ephraim McDowell, of Danville, Kentucky, in 1809, and the tying of the great arteries. The operation of lithotrity, for removing stone from the bladder by crushing the stone, was introduced by Civiale, 1817-1824, who devised successful instruments and modes of using them. In 1836 to 1840 Richard Bright, an English physician, made important researches and discoveries in relation to the functions and diseases of the kidneys, and established the nature of the so-called "Bright's disease."

[Ill.u.s.tration: FIG. 175.--VERDIN'S SPHYGMOMETROGRAPH, FOR RECORDING THE ACTION OF THE PULSE.]

_Schools of Medicine._--While the regular school of medicine (called by some "Allopathy") has held the leading place in medicine, various other schools have sprung up in the Nineteenth Century, all of which represent advances in a knowledge of the laws of health, and the modes of preventing and curing diseases. Hahnemann, in his "_Organon der Rationellen Heilkunde_," in 1810, gave h.o.m.opathy its name, and reduced it to a system. The doctrine of _similia similibus curantur_ (like cures like), has gained great popularity in the latter part of the century.

Hydropathy, as a school, also made its appearance in the early part of the Nineteenth Century. Priessnitz was its first disciple, and the _Grafenberg cure_, established in 1826, was a noted inst.i.tution for many years. The useful application of water in the form of baths and cold packs, has been known for centuries, and will always be used as a valuable agency in sickness and in health. The "Thompsonian" system of treating diseases was covered by patents in 1813, 1823 and 1836, and attained considerable notoriety in the early half of the century.

Sweating by hot bricks and hot tea made of "Composition Powders,"

vomiting with lobelia to produce relaxation, and a fiery liquid for cramps, called "No. 6," were the chief remedies, and very few boys who had once taken the treatment were ever willing afterwards to admit that they were sick. In the latter part of the Nineteenth Century _electro-therapeutics_ has received a large share of attention, many forms of medical batteries have been devised, and probably no more promising field of study and research exists in the whole domain of medicine.

_Dentistry._--George Washington had false teeth, and it is said that the teeth of some of the mummies of Egypt had gold fillings, but it remained for the Nineteenth Century to establish dentistry as an art, and its influence in securing better mastication and digestion of food, more sanitary mouths and shapely faces, cannot be estimated. Few people can be found to-day who have not either filled teeth, bridge work, gold caps, or artificial sets of teeth. The most important advance in the art was in the invention of the rubber plate for holding the porcelain teeth. This was the invention of J. A. c.u.mmings, and was covered by him in his patent No. 43,009, June 7, 1864. In more recent years "bridge-work" represents the most important advance. In this practice one or more artificial teeth are firmly held in the place of missing teeth by a strong bridge-piece of metal, which at its ends is anch.o.r.ed to the adjacent natural teeth. This was first done by Bing (British Pat.

No. 167, of 1871), and was afterwards patented in somewhat different form in the United States by J. E. Lowe, No. 238,940, March 15, 1881, No. 313,434, March 3, 1885, and Richmond, May 22, 1883, No. 277,933.

Porcelain and gold crowns and dental pluggers run by electricity represent other important advances in this art. It is said that there are 20,425 dentists in the United States, and that in 1899 they employed in their practice 20,499,000 false teeth.

_Artificial Limbs._--With the successful work of the surgeon came the effort to repair, as far as possible, the loss of the limb. Until about the middle of the Nineteenth Century the survivor of an operation was an unsymmetrical, unique, and pitiful object. The peg-leg of Peter Stuyvesant lives in history, and the arm-hook of Capt. Cuttle is familiar to every reader. The first United States patent for an artificial leg was granted to B. F. Palmer, Nov. 4, 1846, No. 4,834.

Wooden legs with a restricted back and forward ankle motion and a spring, were constructed by A. A. Marks from 1853 to 1863. On Dec. 1, 1863, a patent, No. 40,763, was granted to Mr. Marks for the use of sponge rubber for constructing artificial feet and hands that dispensed with the articulated joints, and made a great improvement. In patent No.

366,494, July 12, 1887, to G. E. Marks, the foot and leg portion of a wooden leg are made from wood which grows with a crook, as at the root of a tree, where the strength and lightness of a continuous natural grain is obtained at the instep. About 300 patents have been granted for artificial legs and arms. Modern improvements have extended to every detail of construction, and so perfect to-day is the average wooden leg that it is hardly to be detected. Men with wooden legs ride horseback, are expert users of the bicycle, and have even performed feats on the tight rope. The inventor's genius has not stopped at repairing limbs, however, for artificial eyes, artificial ear drums, the audiphone, foot extensions for short legs, crutches, braces, abdominal supporters, and various other applications to supplement the defects of the body have been devised.

_Digestion._--The physiology of digestion had, perhaps, the first real light shed upon it by Beaumont's observations from 1825 to 1832. A Canadian boatman, Alexis San Martin, was wounded in the abdomen from a charge of buckshot, and the wound healed, leaving a permanent opening in the stomach, through which the operation of digestion could be observed.

This furnished visible evidence of the relative digestibility of different kinds of foods, and the general functions of the stomach. The peculiar and different conditions governing the digestion of the starch foods, the alb.u.menoids (such as meat and fish), and the sugars and fats, have been clearly ascertained, and "what is one man's food is another man's poison" is now susceptible of intelligent diagnosis and effective adjustment. Of late years the stomach has been greatly aided in its functions by prepared or predigested foods. The action of diastase, in converting starch into grape sugar, has been taken advantage of, and cereals treated with diatase, malted milk, lactated and peptonized foods, have proven a boon to the enfeebled digestion, while the intelligent study of dietetics has done much to relieve the physician and promote the health of the individual by right living.

_Bacteriology._--Although Leeuwenhoeck discovered the bacterium in 1668-1675, up to 100 years ago disease and death were largely regarded as dispensations of Providence, and with fatuous resignation were accepted as inevitable. The microscope and the study of bacteriology, however, have revealed to us the presence of minute living organisms or germs, which are everywhere around us, infesting the air, the earth, the water, our food, our bodies, and all organic matter in countless millions. These infinitely small beings multiply with a rapidity and fecundity that bewilders the imagination. Their method of multiplication is by fissiparism--that is to say, each splits into two independent beings that separate and afterwards lead independent lives. It is said that there is one species in which not more than six or seven minutes are required for the division to take place. A single individual might consequently produce more than a thousand offspring in an hour, more than a million in two hours, and in three hours more than the number of inhabitants on the globe. They are known as micro-organisms, of which the bacteria are the most important. The bacteria are further divided into species, and names are given them to distinguish the different forms. The little rod-shaped ones are called _bacilli_: the spheroidal ones _micrococci_ or _cocci_. If they cling together in chains they are called _streptococci_; if of a spiral or corkscrew form they are called _spirallae_. The curved bacilli are called "_comma_" _bacilli_, from their resemblance to the punctuation mark of that name. The presence of peculiar forms of these bacteria in diseases has so suggested the relation of cause and effect as to have given rise to the so-called "germ theory" of disease. Now we know with reasonable certainty that cholera, diphtheria, typhoid fever, whooping cough, mumps, cerebro-spinal meningitis, pneumonia, tuberculosis, hydrophobia, and many other diseases have each its specific cause in the form of a microbe.

[Ill.u.s.tration: FIG. 176.

BACILLUS OF TUBERCULOSIS IN SPUTUM. BACILLUS OF DIPHTHERIA (KLEBS-LOEFFLER).

BACILLUS OF TYPHOID FEVER.

(Photo-Micrographs, 1,000 diam., by William M. Gray, M. D.)]

[Ill.u.s.tration: TERTIAN FORM. AESTIVO-AUTUMNAL FORM.

FIG. 177.--BLOOD OF MAN. SHOWING PARASITE OF MALARIA (LAVERAN).

(Photo-Micrographs, 1,000 diam., by William M. Gray, M. D.)]

Henle, a German physiologist, as early as 1840, maintained the doctrine of _contagium vivum_, or contagion by the transmission of living germs.

Certain cla.s.ses of diseases have also long been known as zymotic, or ferment diseases. Louis Pasteur's work, however, marks the first definite and important results in the study of bacteriology, and he is the father of the "germ theory" of disease. He exploded the previously held theories of scientists concerning the spontaneous generation of living things, and clearly established and promulgated the knowledge of disease germs. Commencing his great work about 1865 with the investigation of the silk worm plague in France, he discovered it to be due to parasites, and checked it. He also gave great attention to the subject of fermentation, proving it to be caused by micro-organisms.

Taking up the diseases of men and animals, he gave practical value to the truths of his theory in the treatment of hydrophobia, diphtheria, and other diseases, using the principle of vaccination to destroy or render innocuous the toxins or disease-producing poisons derived from living germs. Working along the same lines must be mentioned Dr. Koch, whose success in detecting the microbes which cause consumption and cholera has made him famous the world over. Of the great variety of these little microbes which have been separately identified, many are innocuous, and, in fact, subserve many important and useful purposes in nature, while others are to be as much dreaded as the deadly cobra or the rattlesnake. A few typical examples of the latter are given in Figs.

176 and 177, multiplied 1,000 diameters. The ill.u.s.trations represented in Fig. 177 show the parasites that cause malaria, or fever and ague.

The dark bean-shaped cells are the normal blood corpuscles, and the few speckled cells are those infested with the malarial parasites. It is now believed that the mosquito is the active factor in the dissemination of malaria, and it is, therefore, to be remembered that this pestiferous little insect not only inflicts a painful and disagreeable sensation with his puncture, but innoculates the system with poisonous malarial germs at the same time.

[Ill.u.s.tration: FIG. 178.

TUBE CONTAINING CULTURE OF BACILLI OF TUBERCULOSIS.

TUBE CONTAINING CULTURE OF COMMA BACILLI OF CHOLERA.]

For the study of bacteria they are propagated artificially in a test tube--_i. e._, a substance called a "culture" is prepared from some organic material which, like the substances of the human body, is favorable to their propagation. Such culture media are found in beef blood, gelatine, beef extracts, meat broth, milk, etc. An ordinary test-tube is supplied with some of the culture medium, and is then sterilized over the fire to destroy all interfering germs. Material infected with the microbe is then placed in the test-tube by a sterilized platinum wire and the tube closed by raw cotton. It is then placed in an incubator oven and is subjected to a gentle heat. In a little while the microbes begin to develop and increase, forming colonies, in which they swarm by the million, and present the clotted appearance seen in Fig. 178. The separation of different bacteria existing in the same material, so as to isolate each species and get what is called a "pure culture," has been greatly promoted by Prof.

Koch's method of _plate culture_. In this the propagation of bacteria is effected upon a sterilized gla.s.s plate under a bell jar in such a thin layer as to facilitate the segregation of species, enabling them to be counted under the microscope and picked out and sown in another culture to get an unmixed crop of a definite species. Such a culture so multiplies the same microbe, to the exclusion of others, as to permit it to be easily identified and studied.

According to the practice in modern munic.i.p.al health regulations, the test as to when a child recovering from diphtheria is incapable of disseminating the disease is by test culture. A swab of cotton is rubbed against the interior walls of the child's throat to secure the germs (if present), and the swab is then placed in a "culture" in a test-tube and the tube put in an incubator. If, after the period of incubation, no colonies of the germs develop, it is accepted as evidence that the diphtheria germs are no longer present in the throat, and the child is released from quarantine.

It is the presence of these specific microbes in the fluids or solids of the system which const.i.tutes the disease, and for the cure of the same the intelligent physician of to-day looks less to medication, and more for some agent that will destroy the germ, neutralize its effect, or render the body tolerant thereto. Out of the knowledge of disease germs has grown the great era of antiseptic surgery, inaugurated by Sir Joseph Lister, about 1865. Carbolic acid, the bichloride of mercury, and formalin are the most efficient weapons against the dreaded microbe.

To-day every surgeon in the civilized world sterilizes his knife, and conducts the treatment of wounds and all operations by antiseptic methods, in accordance with a knowledge of the deadly influence of the ubiquitous microbe, and the result has been to so reduce the risk to life that even capital operations are no longer coupled with the apprehensions of death. Every hospital, board of health, and organized medical and sanitary body predicates its laws and modes of treatment upon the principles of bacteriology.

_House Sanitation._--The permanent home of the microbe is the sewer, and sanitary plumbing, designed to exclude from the house the germ-laden and disease-breeding gases from the sewer, const.i.tutes one of the great advances of the century. About 3,500 patents have been granted for water closets and bath appliances, and about 900 patents on sewerage alone, the most of which are directed to improved conditions of sanitation.

[Ill.u.s.tration: FIG. 179A.--STREET CONNECTIONS, MODERN SANITARY HOUSE PLUMBING.]

[Ill.u.s.tration: FIG. 179.--MODERN SANITARY HOUSE PLUMBING.]