INTRODUCTION. n 



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 90 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 



