QUANTITY OF CULTURE INOCULATED 171 



septically and compression is made central to the point of injection. 

 In large animals it may be advantageous, first, to expose the vein by 

 an incision in the skin and fascia. If this is necessary, it must, of 

 course, be done with sterile instruments. Rabbits are generally 

 inoculated intravenously through the large veins of the ear. The 

 posterior vein is better adapted for injections than the larger anterior. 

 The injection is made from the external surface of the ear, where the 

 hair should be clipped in order to facilitate sterilization and also the 

 finding and proper compression of the vein. It is best to use a small, 

 short injection needle. Blood may also be withdrawn by this same 

 method. This is necessary in cases where the immunizing serum of 

 a treated rabbit is tested before finally killing it and collecting all the 

 serum. 



Intraperitoneal Inoculation. This is very frequently practised in 

 bacteriologic tests. In addition to the usual asepsis, it is important to 

 make the injection in such a manner as not to injure the intestines. 

 This may be accomplished by either one of two methods. One is by 

 the use of dull needles, which require a preliminary incision through 

 the skin and fascia in the median line of the anterior abdominal wall. 

 The needle is then pushed right in the median line through the peri- 

 toneum and the overlying tissues. In the other method the animal 

 is placed hind legs upward, a position in which the intestines fall 

 toward the diaphragm. If the needle is introduced in the middle line 

 below the umbilicus, and held very obliquely so that it does not pene- 

 trate very far into the abdominal cavity, the danger of injuring the 

 intestines or any of the abdominal viscera is reduced to a minimum. 



Other Forms of Inoculation. Inoculations are occasionally made in 

 the thoracic cavity through an intercostal space, but more frequently 

 in the anterior chamber of the eye, where the developing lesions can 

 be studied directly from day to day. Subdural inoculations are made 

 after preliminary incision in the scalp and trephining of the skull. 

 Injections into the spinal canal may be made in the lumbar region, 

 by inserting a long needle of the hypodermic syringe into the canal, 

 between two vertebrae, laterally from the median line. 



Infections of the Intestinal tract are made by feeding animals with 

 the infected material. If it is desirable to introduce such material 

 directly into the intestines, it is necessary to perform a laparotomy, 

 exposing the duodenum, into which the injection is made directly 

 with a very small hypodermic syringe. 



Animals are sometimes infected experimentally through the res- 

 piratory tract. This is done by connecting their cages, directly or 

 indirectly, with a spraying apparatus which disseminates the infected 

 material. 



Quantity of Culture Inoculated. It is generally desirable, except in 

 purely diagnostic work, to use a definite quantity of the pure culture 

 for inoculation. This may be accomplished by a variety of methods: 

 (1) A pure culture is prepared by inoculating 10 c.c. of bouillon. 



