EXPERIMENTS UPON ANIMALS. 73 



first been introduced in the eye. The material is passed 

 through the opening with a small forceps, and with a few strokes 

 of a spoon it is pushed in the anterior chamber. 



For the cornea a few scratches made in the corneal tissue 

 will suffice ; the material is then gently rubbed in. 



Inoculation of the Cerebral Membranes. The skin and 

 aponeurosis cut through where the skull is the thinnest. Then 

 the bone carefully trephined, and the dura exposed. In Rabies 

 inoculation, the syringe containing the hydrophobic virus pierces 

 the dura and arachnoid, and the virus is discharged beneath the 

 latter. 



Intra-Tracheal. The bacteria can be introduced directly into 

 the trachea, thus coming in contact with the lungs. 



Intra-duodenal. Cholera germs are injected into the intes- 

 tines after they have been exposed, by carefully opening the 

 abdomen. This is done in order to avoid the action of the 

 gastric juice. 



Obtaining Material from Infected Animals. The animal 

 should be skinned, or the hairs plucked out, before it is washed, 

 at least the portion where the incision is to be made. Then the 

 entire body is washed in sublimate. Two sets of instruments 

 are required, one for coarser and one for finer work : the one 

 sterilized in the flame ; the other, to prevent being damaged, 

 heated in a hot air oven. 



The animal, the mouse for example, is stretched upon a board, 

 a nail or pin through each leg, and the head fixed with a pin 

 through the nose. The skin is dissected away from the belly 

 without exposing the intestines. Then the ribs being laid bare, 

 the sternum is lifted up, and the pericardium exposed. A pla- 

 tinum needle dipped into the heart after the pericardium has 

 been slit will give sufficient material for starting a culture. If 

 the other organs.'are to be examined, further dissection is made. 

 If the intestines were first to be looked at, they would be laid 

 bare first. 



In this manner material is obtained, and the results of inocu- 

 lation noted. 



Frequent sterilization of the instruments is desirable. 



