120 MICROSCOPIC METHODS. 



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 be^t. They can easily be sterilised by boiling them in the 

 large fisi > -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 

 5 min. clinical variety) is smeared with vaseline, 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, again 

 remaining 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. 



Autopsies on Animals dead or killed after Inoculation. 

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

 necessary to have some shallow troughs, constructed either of 

 metal or of wood covered with metal, conveniently with sheet 

 lead, and having a perforation at each corner to admit a tape or 

 strong cord. The animal is tightly stretched out in the trough 

 and tied in position. The size of the trough will, therefore, have 

 to vary with the size of the outstretched body of the animal to 

 be examined. In certain cases it is well to soak the surface of 

 the animal in carbolic acid solution (i to 20), or in corrosive 



