TEXT-BOOK OF BACTERIOLOGY. 157 



majority of cases it will be a question of undoubted and immediate 

 phenomena of poisoning-. And what degree of value can be at- 

 tached to experiments in which such tiny creatures as mice receive 

 several degrees of fluid from a Pravaz syringe injected into the 

 thorax ? No wonder that they perish after it. The diminutiveness 

 of all the proportions makes it almost impossible to inject the 

 material into the pleura! cavity alone. One penetrates also into the 

 lungs, and indeed it is somewhat similar to injecting three or four 

 litres of some liquid into the human respiratory organs by means 

 of a fire-engine. It is high time that these mouse experiments 

 should be confined within the limits of true usefulness. 



If bacteria are to be brought into the organism by way of 

 the digestive organs, they can be administered along with the food, 

 or they may be brought direct into the stomach by the cesophageal 

 probang, or into the intestines per anum. With rabbits the former 

 process is easy; the catheter is put into the lateral gap between 

 the teeth and cautiously pushed further; with Guinea-pigs the two 

 rows of teeth must be held apart by a perforated wooden gag, and 

 one must be particularly careful not to employ too much force, as 

 otherwise the epiglottis is easily pushed aside and one penetrates 

 into the lungs instead of the stomach. 



If we wish to cause absorption of virus through the lungs, we 

 should employ the inhalation method. The best process is that 

 described by Buchner, which approaches more nearly the natural 

 course of things. The material to be inoculated is diluted with 

 sterilized water or bouillon poured into a spray apparatus and 

 thence dispersed into the air. The spray thus produced is, how- 

 ever, so dense that the animals, if directly exposed to it, become 

 dripping wet and are apt to swallow a considerable portion of the 

 virus. Buchner, therefore, places the entire spray apparatus in a 

 vessel of considerable size for instance, in a WoulfFs flask or a 

 wide test-tube with a doubly-perforated India-rubber stopper, and 

 conducts the exceedingly fine vapor which comes out, by means of 

 a tube, into the closed box containing the animals to be experi- 

 mented upon. The list of means at our disposal for conducting 

 experiments of transmission has by no means been exhausted, but 

 they will be found to depend, one and all, on the principles enumer- 

 ated, and we may therefore be excused from going into all the 

 possible details. 



Of course the most careful observation of all those precautions 

 of bacteriological manipulation which should in no case be neg- 

 lected >s doubly necessary here. 



At the place where the animals are to be inoculated hairs 



