INTRODUCTION. Tt 
formal-bichromate injected into the third ventricle by push- 
ing the cannula about half an inch through the infun- 
dibulum (Fig. 90). The brain of a sheep or calf will be 
very soft when removed, as it cannot be hardened pre- 
viously by injecting the hardening fluid into the arteries. 
Therefore it is necessary to lay the specimen on absorbent 
cotton in the jar of formal-bichromate, which must be 
exchanged for fresh fluid on the second and third days. 
At least two weeks are required for hardening the brain of 
a sheep or calf, after which it is placed in 5% formalin 
for a week or more to wash out the bichromate before 
dissection. Brains are best preserved permanently in 85% 
alcohol. 
Preparation of the Osseous System.—A mounted skele- 
ton of the cat may be purchased for about eight dollars. It 
is far more satisfactory, however, to use the disarticulated 
bones for study. These are easily prepared in the follow- 
ing manner: As soon as the animal is dead, the skin and the 
greater part of the flesh should be cut away and the internal 
organs removed. The bones with much flesh remaining on 
them are then put into 7000 c.c. of water containing 150 
grams of gold dust. This may then be boiled from two to 
four hours but better results are given by using the low 
flame and keeping the solution at a temperature between 
75 and oo degrees centigrade from 3 to 6 hours. As soon 
as the flesh falls freely off the bones they should be brushed 
clean in a pan of water and the brain broken to pieces with 
a bent wire thrust into the foramen magnum. The con- 
tents of the skull may then be washed out under the tap. 
This treatment renders the bones perfectly clean, white and 
free from grease. 
By heating the bones from one to two hours only and 
not allowing the temperature to rise above 85 degrees, the 
flesh may be brushed from the limbs without removing the 
