The Elements of Bacteriological Technique Part 104

[Ill.u.s.tration: FIG. 197.--Apparatus for post-mortem examination, animal on board.]

3. Drench the fur (or feathers) with lysol solution, 2 per cent. This serves the twofold purpose of preventing the hairs from flying about and entering the body cavities during the autopsy, and of rendering innocuous any vermin that may be present on the animal.

[Ill.u.s.tration: FIG. 198.--Searing iron.]

4. Examine the cadaver carefully. Recollect that laboratory animals are not always hardy; death may be due to exposure to heat or cold, to starvation or over- or improper feeding or to the attack of rats--and not to the bacterial infection.

5. Fasten the body of the animal, ventral surface upward (unless there is some special reason for having the dorsum exposed), out on a board by means of copper nails driven through the extremities.

6. With sterile forceps and scalpel incise the skin in the middle line from the top of the sternum to the p.u.b.es. Make other incisions at right angles to the first out to the axillae and groins, and reflect the skin in two lateral flaps. (Place the now infected instruments on the board by the side of the body or support them on a porcelain knife rest.)

~Seat of Inoculation.~--

7. Inspect the seat of inoculation. If any local lesion is visible, sear its exposed surface and with the platinum loop, remove material from the deeper parts to make tube and surface plate cultivations and cover-slip preparations.

Collect specimens of pus or other exudation in capillary pipettes for subsequent examination.

8. Inspect the neighbouring lymphatic glands and endeavour to trace the path of the virus.

9. Sear the whole of the exposed surface of the thorax with the searing irons.

~Pleural Cavity.~--

10. Divide the ribs on either side of the sternum and remove a rectangular portion of the anterior chest wall with sterile scissors and a fresh pair of forceps, exposing the heart. Place the infected instruments by the side of the first set.

11. Observe the condition of the anterior mediastinal glands, the thymus and the lungs. Collect a quant.i.ty of pleuritic effusion, if such is present, in a pipette for further examination later.

12. Raise the pericardial sac in a fresh pair of forceps and burn through this structure with a searing iron.

Collect a sample of pericardial fluid in a pipette for microscopical and cultural examination.

13. Grasp the apex of the heart in the forceps and sear the surface of the right ventricle.

14. Plunge the open point of a capillary pipette through the seared area into the ventricle and fill with blood.

Make cultivations and cover-slip preparations of the heart blood.

15. Collect a further sample of blood or serum for subsequent investigation as to the presence of antibodies.

~Peritoneal Cavity.~--

16. Sear a broad track in the middle line of the abdominal wall; open the peritoneal cavity by an incision in the centre of the seared line.

Observe the condition of the omentum, the mesentery, the viscera and the peritoneal surface of the intestines.

17. Collect a specimen of the peritoneal fluid (or pus, if present) in a capillary pipette. Make cultivations, tube and surface plate, and cover-slip preparations from this situation.

18. Collect a specimen of the urine from the distended bladder in a large pipette (in the manner indicated for heart blood), for further examination, by cultivations, microscopical preparations, and chemical a.n.a.lysis.

19. Collect a specimen of bile from the gall bladder in similar manner.

20. Excise the spleen and place it in a sterile capsule. Later, sear the surface of this organ; plunge the spear-headed spatula through the centre of the seared area, twist it round between the finger and thumb, and remove it from the organ. Sufficient material will be brought away in the eye in its head to make cultivations. A repet.i.tion of the process will afford material for cover-slip preparations.

21. Seize one end of the spleen with sterile forceps. Sear a narrow band of tissue, right around the organ and divide the spleen in this situation with a pair of scissors. Holding the piece of spleen in the forceps, dab the cut surface on to a surface plate in a number of different spots.

22. In like manner examine the other organs--liver, lungs, kidneys, lymphatic glands (mesenteric, hepatic, lumbar, etc), etc. Prepare cultivations and cover-slip preparations.

23. Dissect out a long bone from one upper and one lower limb and one of the largest ribs. Prepare cultures from the bone marrow in each case.

Set aside these bones for the subsequent preparation of marrow films.

24. Film preparations of bone marrow are best made by the Price-Jones method. Seize the bone in a pair of pliers and squeeze out some of the marrow; receive it in a platinum loop, and transfer to a watch gla.s.s of dissociating fluid and emulsify. The dissociating fluid is a neutral 10 per cent. solution of glycerine prepared as follows:--

Measure out 10 c.c. Price's best glycerine and 90 c.c.

sterile ammonia-free distilled water. Mix. t.i.trate against n/10 sodic hydrate solution using phenolphthalein as the indicator. The initial reaction is usually + 0.1 to + 0.5; add the calculated amount of n/10 sodic hydrate solution to neutralise.

25. Place a loopful of fresh desiccating fluid on a 3 1 gla.s.s slide; add a similar loopful of the marrow emulsion, and spread very gently over the surface of the slip.

26. Allow film to dry in the air (protected from dust) without heating.

27. Stain with Jenner's polychrome stain (page 97) for two and a half minutes.

28. Wash with ammonia-free distilled water, dry thoroughly and mount in xylol balsam.

~Cranial and Spinal Cavities.~--

29. In some instances it may be necessary (e. g., experimental inoculation of rabies) to examine the cranial cavity or to remove the spinal cord. Return the viscera to the abdominal cavity; draw the flaps of skin together and secure with Michel's steel clips. Draw the copper nails securing the limbs to the board, reverse the animal and again nail the limbs down--the body now being dorsum uppermost.

30. Make a longitudinal incision in the mesial line from snout to root of tail, and four transverse incisions--one joining the roots of the two ears, one across the body at the level of the spinis of the scapulae, another at the level of the costal margin and the last across the upper level of the pelvis. Reflect these flaps of skin.

31. With forceps and scalpel dissect out the muscles lying in the furrow on either side of the spinal processes.

32. Cut through the bases of the transverse processes with bone forceps.

Cut away the vault of the skull, cut through the roots of the nerves and remove the brain and spinal cord, place in a large gla.s.s dish for examination. Prepare cultivations from the cerebro-spinal fluid. The removal of the brain and cord is a tedious process and during the dissection it is difficult to avoid injury to these structures.

The operation is, however, carried out very expeditiously and neatly with the aid of the surgical engine (_vide_ page 361). A small circular saw is fitted to the hand piece. The bones of the skull are cut through and the whole of the vault removed, exposing the entire vertex of the brain. Similarly all the spinous processes can be removed in one string by running the saw down first one side of the spinal column and then the other. In this way ample s.p.a.ce for the removal of the nervous tissues is obtained with a minimum of labour.

33. Having completed the preparation of cultures remove small portions of various organs at leisure and place each in separate bottles of fixing fluid for future sectioning. Affix to each bottle a label bearing all necessary details as to its contents.

34. If necessary, remove portions of the organs for preservation and display as museum specimens (_vide_ page 404).

35. Gather up all the infected instruments, return them to the steriliser, and disinfect by boiling for ten minutes.

[Ill.u.s.tration: FIG. 199.--Spear-headed platinum spatula (actual size.)]

36. Sprinkle dry sawdust into the exposed body cavities to absorb blood and fluid. Cover the body with blotting or filter paper, moistened with 2 per cent. lysol solution. Place in a galvanised iron pail, provided with a lid, ready for transport to the crematorium.