Animal Inoculations 271 



conspicuous and accessible (Fig. 74). A peculiar and im- 

 portant fact to remember is that the less conspicuous poste- 

 rior -vein of the ear is much better adapted to the purpose 

 than the anterior. The introduction of the needle should be 

 made from the hairy external surface of the ear when the 

 vein is immediately beneath the skin. 



If the ear be manipulated for a moment or two before the 

 injection, vasomotor dilatation occurs and the blood-vessels 

 become larger and more conspicuous. The vein should be 

 compressed at the root of the ear until the needle is intro- 

 duced, and the injection made as near the root as possible. 

 The fluid should be slowly injected. 



Bacteria can be introduced into the lymphatics only by 

 injecting liquid cultures of them into some organ with com- 

 paratively few blood-vessels and large numbers of lym- 

 phatics. The testicle is best adapted to this purpose, the 

 needle being introduced deeply into the organ. 



Sometimes subcutaneous inoculations are made by intro- 

 ducing the platinum wire through a small opening made in 

 the skin by a snip of the scissors. By this means solid 

 cultures from agar-agar, etc., can be introduced. 



Intra-abdominal and intrapleural injections are some- 

 times made, and in cases where it becomes necessary to 

 determine the presence or absence of the bacilli of tuber- 

 culosis or glanders in fragments of tissue it may be neces- 

 sary to introduce small pieces of the suspected tissue 

 under the skin. To do this the hair is closely cut over 

 the point of election, which is generally on the abdo- 

 men near the groin, the skin picked up with forceps, a 

 snip made through it, and the points of the scissors intro- 

 duced for an inch or so and then separated. By this man- 

 oeuver a subcutaneous pocket is formed, into which the 

 tissue is easily forced. The opening should not be large 

 enough to require subsequent stitching. 



When tissue fragments or collodion capsules are to be in- 

 troduced into the abdominal cavity, the animal should be 

 anesthetized and a formal laparotomy done, the wound being 

 carefully stitched together. 



When, in studying Pfeiffer's phenomenon and similar con- 

 ditions, it is desirable occasionally to withdraw drops of 

 fluid from the abdominal cavity, a small opening can be 

 burned through with a blunt needle. This does not heal 



