134 BACTERIOLOGY 



these animals by intracardiac injection. For this purpose the 

 animal is etherized and the precordial region is shaved and dis- 

 infected. The material to be injected is taken up into a Luer 

 glass syringe. A second syringe, empty, with needle attached, 

 is used to puncture the chest wall and the heart, preferably the 

 wall of the right ventricle. The needle is introduced in the inter- 

 costal space directly over the heart and near the border of the 

 sternum. The appearance of blood in the previously empty 

 syringe gives notice that the cavity of the heart has been entered. 

 The syringe is now detached from the needle and the other 

 syringe which contains the material to be injected is quickly 

 substituted for it. The injection is made slowly. 



Other Sites for Inoculation. Many other regions are easily 

 reached with the injection needle, such as the pleural cavity, the 

 chambers of the eye, the spinal canal, the interior of muscles, 

 and the substance of the testis. 



Subcutaneous Application. Inoculation may be accomplished 

 without using a syringe if desired. The skin and mucous mem- 

 branes may be scratched with a needle or other instrument and 

 the infectious material applied to the slight wound thus made. 

 A small pocket may be made under the skin by making a small 

 incision and introducing a blade of the forceps to separate the 

 skin from the underlying muscle; and into such a pocket one may 

 introduce solid material, bacteria from a culture, pieces of tissue, 

 garden soil or splinters of wood, ^with accompanying bacteria. 

 The opening of the pocket is closed by cauterization or sealed 

 with collodion 



Alimentary and Respiratory Infection. Animals are some- 

 times infected by feeding the virus, occasionally by injection 

 into the rectum. Infection of the respiratory tract by spraying 

 infectious material^m the air breathed by the animal is rarely 

 employed. 



Collodion Capsules. Bacteria may be cultivated in the 

 living body of an animal, without infecting the animal, when they 

 are enclosed in collodion capsules. Their soluble products are 



