EXPERIMENTATION UPON ANIMALS. 223 



is much better adapted to the purpose than the anterior. 

 The introduction of the needle should be made from the 

 hairy surface of the 

 ear. 



If the ear is manip- 

 ulated for a moment or 

 two before the injec- 

 tion is begun, vaso- 

 motor dilatation 

 occurs and the blood- 

 vessels all become 

 larger and more con- 

 spicuous. The vein 

 should be compressed 

 at the root of the ear 

 until the needle is in- 

 troduced, and the in- 

 jection made as near * IG - 4 1 - — Method of making an intravenous 



the root as possible. in J ectio " into a rabblt \ ? bserv 1 e tbat the n ! edle 



. , . - enters the posterior vein from the hairy surface. 



The introduction of 

 bacteria into the lymphatics is only possible by injecting 

 liquid preparations 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 the inoculation can be made by the platinum 

 wire, a very small opening made in the skin by a snip of 

 the scissors being sufficient. 



Sometimes intra-abdominal and intra-pleural injections 

 are made, and in cases where it becomes necessary to 

 determine the presence or absence of tuberculosis or 

 glanders in tissues it may be necessary to introduce small 

 pieces of the suspected tissue under the skin or into the 

 abdominal cavities. To do this is not difficult. The 

 hair is carefully, closely cut over the point of election, 

 which is generally on the abdomen near the groin, the 

 skin picked up with forceps, a snip made through it, 

 and the points of the scissors introduced for half an inch 



