EXPERIMENTS UPON ANIMALS. 99) 
Large quantities of fluid may be injected into the cavity of the 
abdomen or into the circulation by slowly forcing the fluid through 
a slender canula, properly introduced, which is coupled with a large 
syringe by means of rubber tubing, or with a glass receptacle from 
which the fluid is forced by the pressure of air pumped in with a 
rubber hand ball. 
Mice are usually injected subcutaneously near the tail. The 
little animal is first seized by a long pair of forceps, or ‘‘ mouse 
tongs,” and the hair is clipped away on the back just above the tail. 
If solid material is to be introduced a little pocket is made with scis- 
sors or with a lancet, into which the infectious material is carried by 
means of a platinum needle or slender forceps. Liquids may be in- 
jected by the little glass syringe heretofore described, the point of 
which is easily forced through the skin. 
Pasteur’s method of inoculating rabbits with the virus of hydro- 
phobia consists in trephining the skull and injecting the material 
beneath the dura mater. An incision through the skin is first made 
to one side of the median line a short distance back of the eyes. 
The edges of the wound are separated, and a small trephine (five or 
six millimetres in diameter) is used to remove a button of bone. The 
emulsion of spinal cord from a hydrophobic animal is then carefully 
injected beneath the dura mater—two or three drops will be sufficient. 
The wound is washed out with a two-per-cent solution of carbolic 
acid and closed with a couple of sutures. 
Injections into the intestine are made by carefully opening the 
abdomen with antiseptic precautions, gently seizing a loop of the in- 
testine, and passing the point of the syringe through its walls; the 
loop is then returned and the incision in the walls of the abdomen 
carefully closed with sutures and dressed antiseptically. 
Inoculations into the anterior chamber of the eye of rabbits and 
other animals have frequently been practised, and offer certain ad- 
vantages in the study of the local effects of pathogenic microérgan- 
isms. The animal should be fastened to an operating board, belly 
down, and its head held by an assistant, who at the same time holds 
the eyelids apart. The conjunctiva is seized with forceps to steady 
the eye, and an incision about two millimetres long is made through 
the cornea with a cataract knife. Through this opening a small 
quantity of a liquid culture may be injected, or a bit of solid material 
introduced with slender curved forceps. 
Ordinary injections give but little pain and do not call for the use 
of an anesthetic. When anesthesia is required ether will usually 
be preferable to chloroform. Rabbits, especially, are very apt to die 
from chloroform, no matter how carefully it may be administered. 
Dogs, rats, and mice stand ether very well. The smaller animals 
