138 BACTERIOLOGY 



by intracardiac injection. For this purpose the animal is etherized 

 and the precordial region is shaved and disinfected. 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 accompHshed 

 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 in 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 



