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 glass 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. Titrate 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 x 1 glass 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 bra