188 BACTERTOLOar. 



the animal stretched upon its back on a table, is the 

 usual position for the operation when practised upon 

 guinea-pigs and rabbits. The point at which the inoc- 

 ulations are commonly made is in the abdominal walls 

 either to the right or left of the median line and about 

 3 cm. distant. When pigeons are used they are held 

 with the legs, tail, and ends of the wings in the one 

 hand, and the head and anterior portion of the body 

 in the other, leaving the area occupied by the pectoral 

 muscles, over which the inoculation is to be made, free 

 for manipulation. The hair should be closely cut with 

 the scissors in the case of the guinea-pigs and rabbits, 

 and the feathers pulled out in the case of the pigeon. 



Injection into the Circulation. — It is not infre- 

 quently desirable to inject the material under considera- 

 tion directly into the circulation of an animal. If the 

 rabbit is to be employed for the purpose, the operation 

 is usually done upon one of the veins in the ear. 



To those who have had no practice in this procedure 

 it offers a great many difficulties ; but if the directions 

 which will be given are strictly observed, the greatest 

 of these obstacles to the successful performance of the 

 operation may be overcome. 



When viewing the circulation in the ear of the rabbit 

 by transmitted light, three conspicuous branches of the 

 main vessel (vena auricularis posterior-) will be seen. 

 One runs about centrally in the long axis of the ear, 

 one runs along its anterior margin, and one along its 

 posterior margin. The central branch (the ramus ante- 

 rior of the vena auricularis posterior) is the largest and 

 most conspicuous vessel of the ear, and is, therefore, 

 selected by the inexperienced as the branch into which 

 it would appear easiest to insert a hypodermatic needle. 



