146 INOCULATION OF ANIMALS 



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 from above. Otherwise material which may be 

 infective may be scratched out of the cage by the animal. The 

 general condition of the animal is to be observed, how far it 

 differs from the normal, whether there is increased rapidity of 

 breathing, etc. The temperature is usually to be taken, This 

 is generally done per rectum. The thermometer (the ordinary 

 clinical variety) is smeared with vaselin, and the bulb inserted 

 just within the sphincter, where it is allowed to remain for a 

 minute ; it is then pushed well into the rectum for five minutes. 

 If this precaution be not adopted a reflex contraction of the 

 vessels may take place, which is likely to vitiate the result by 

 giving too low a reading. 



Collodion Capsules. These have been used to allow the 

 sojourn of bacteria within the animal body without their coming 

 into contact with the cells of the tissues. Various substances 

 in solution can pass in either direction through the wall by 

 diffusion, but the wall is impermeable alike to bacteria and 

 leucocytes. The following method of preparing such capsules is 

 that of M'Rae modified by Harris : A gelatin capsule, such as 

 is used by veterinary surgeons, is taken, and in one end there 

 is fixed a small piece of thin glass tubing by gently heating the 

 glass and inserting it. The tube becomes fixed when quite cold, 

 and the junction is then painted round with collodion, which 

 is allowed to dry thoroughly. The bore of the tubing is cleared 

 of any obstructing gelatin, and the whole capsule is dipped into 

 a solution of collodion so as to coat it completely. The collodion 

 is allowed to dry, and the coating is repeated ; it is also advis- 

 able to strengthen the layer by further painting it at the 

 extremity and at the junction. The interior of the capsule is 

 then filled with water by a fine capillary pipette, and the capsule 

 is placed in hot water in order to liquefy the gelatin, which 

 can be removed from the interior by means of the fine pipette. 

 The sac is filled with bouillon and is placed in a tube of 

 bouillon. It is then sterilised in the autoclave. A small 



