122 INOCULATION OF ANIMALS 



ordinary needle. The mode of procedure is similar, but after 

 the needle is plunged through the abdominal fold, it is partially 

 withdrawn till the point is felt to be free in the peritoneal 

 cavity when the injection is made. There is little risk of 

 injuring the intestines by either method. 



4. Intravenous Injection. The vein most usually chosen is 

 one of the auricular veins. The part has the hair removed, the 

 skin is purified, and the vein made prominent by pressing on it 

 between the point of inoculation and the heart. The needle is 

 then plunged into the vein arid the fluid injected. That it has 

 perforated the vessel will be shown by the escape of a little blood ; 

 and that the injection has taken place into the lumen of the 

 vessel will be known by the absence of the small swelling which 

 occurs in subcutaneous injections. If preferred, the vein may be 

 first laid bare by snipping the skin over it. The needle is then 

 introduced. 



5. Inoculation into the Anterior Chamber of the Eye, Local 

 anesthesia is established by applying a few drops of 2 per cent 

 solution of hydrochlorate of cocaine. The eye is fixed by 

 pinching up the orbital conjunctiva with a pair of fine forceps, 

 and the edge of the cornea being perforated by the hypodermic 

 needle, the injection is easily accomplished. 



Sometimes inoculations are made by planting small pieces of 

 pathological tissues in the subcutaneous tissue. This is especially 

 done in the case of glanders and tubercle. The skin over the 

 back is purified, and the hair cut. A small incision is made with 

 a sterile knife, and the skin being separated from the subjacent 

 tissues by means of the ends of a blunt pair of forceps, a little 

 pocket is formed into which a piece of the suspected tissue is 

 inserted. The wound is then closed with a suture, and collodion 

 is applied. In the case of guinea-pigs, the abdominal wall is to 

 be preferred as the site of inoculation, as the skin over the back 

 is extremely thick. 



Injections are sometimes made into other parts of the body, 

 e.g. the pleurae and the cranium. It is unnecessary to describe 

 these, as the application of the general principles employed above, 

 together with those of modern aseptic surgery, will sufficiently 

 guide the investigator as to the technique which is requisite. 



After inoculation, the animals ought to be kept in comfortable 

 cages, which must be capable of easy and thorough disinfection 

 subsequently. For this purpose galvanised iron wire cages are the 

 best. They can easily be sterilised by boiling them in the large 

 fish-kettle which it is useful to have in a bacteriological laboratory 

 for such a purpose. It is preferable to have the cages opening 



