55 



Anaerobiasis. If it were not for the fact that we have so many facultative anaerobes 

 (organisms growing under anaerobic as well as aerobic conditions) it would be of 

 practical utility to make this biological variation our first step in the study of an 

 unidentified organism. At any rate it is well to remember that the causative organ- 

 isms of plajue, tuberculosisfmfluenza, gonorrjioea. pneumococcal pneumonia and 

 glanders are obligate aerobes ^/vhile those oTftetanus, botulism, gasjfangrene and 

 malignant oedema are obligateanaerobesj The p^ogenic cocci as well as the causa- 

 tive organisms of choleraTtyprioid, parathyphoid and anthrax are facultative anae- 

 robes; they are, however, always studied under aerobic conditions. The colon 

 bacillus as well as organisms of the Friedlander group are also facultative anaerobes. 



Should an organism be encountered in original investigations these 

 requirements as to etiological relationship should be carried out (Koch's 

 postulates) : 



i. The organism should be constantly present in that particular pathological 

 condition. 2. Such bacteria should be isolated in pure culture from the pathologi- 

 cal material. 3. Such pure cultures when inoculated into suitable animals should 

 reproduce the pathological conditions and should be capable of a second isolation in 

 pure culture from such an experimental animal. For various reasons, such as unsuit- 

 able animals or artificial media, these requirements are impossible of execution with 

 several organisms which are generally recognized as the causes of certain diseases. 



ANIMAL EXPERIMENTATION 



The experimental animals most frequently employed in the diagno- 

 sis of bacterial diseases are the guinea-pig, the rabbit, the white rat 

 and the white mouse. In the following diseases the most suitable ani- 

 mals for inoculation are: 



1. Tetanus mice or guinea-pigs, subcutaneously. The spasms begin in the 

 limbs nearest the site of inoculation. 



2. Pneumococci and streptococci mice, intraperitoneally, or rabbits, intraven- 

 ously. 



3. Staphylococci rabbits. 



4. Diphtheria, tuberculosis, anthrax and malignant cedema the guinea-pig, 

 subcutaneously. 



5. Glanders and cholera the guinea-pig, intraperitoneally. 



6. Plague guinea-pigs, cutaneously or subcutaneously. 



In the cutaneous method of infection the material, as from a plague bubo, or the 

 sputum from pneumonic plague, is thoroughly rubbed with a glass rod upon the 

 shaven surface of the guinea-pig. 



In the subcutaneous method one can use a hypodermic needle (the all-glass 

 syringe with platino-iridium needle is the best) or an opening can be cut with the 

 scissors, a pocket then opened up with the forceps and a piece of tissue inserted to 

 the bottom of the pocket with the forceps. 



One can seal the incision with collodion. 



