COLLODION CAPSULES 123 



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 5 min. 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 gelatine 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 gelatine, 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 gelatine, 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 quantity of the 

 bouillon is removed, and the contents are inoculated with the 

 particular bacterium to be studied or an emulsion of the bacterium 

 is added. The glass tubing is seized in sterile forceps and is 

 sealed off in a small flame a short distance above the junction. 

 The closed sac ought then to be placed in a tube of sterile 

 bouillon to test its impermeability. The result is satisfactory if 

 no growth occurs in the surrounding medium. The sac with its 

 contents can now be transferred to the peritoneal cavity of an 

 animal. 



Autopsies on Animals dead or killed after Inoculation. 

 These should be made as soon as possible after death. It is 



