INFECTIONS OF THE DIGESTIVE TRACT 115 



to obtain an idea of the numbers of free spores present. 

 Without this procedure one is apt to underestimate their 

 number. The faecal flora may also be stained directly 

 for capsules by Welch's acetic acid method. 



I shall not attempt here to discuss fully methods of 

 isolation and identification of individual bacteria. The 

 methods generally in use for making plate cultures are 

 those which have been employed. In the case of the 

 bacilli of typhoid fever, dysentery, and allied organisms 

 this subject has already been fully developed by highly 

 trained workers. The study of the diplococci and other 

 coccal forms is one that has been relatively neglected 

 (except in the case of acute infections) and is deserving 

 of much fuller development. On the subject of the anae- 

 robes of the large intestine almost nothing has been done, 

 partly, perhaps, on account of the difficulties of anae- 

 robic technique. Some acute infections with anaerobes 

 have indeed been studied, notably by Tissier and by 

 Klein, but until recently the chronic processes dependent 

 on excessive development of putrefactive anaerobes have 

 escaped attention. The necessity of furnishing anaerobic 

 conditions for the growth of some of these bacteria con- 

 siderably increases the difficulties of identification, but 

 they are by no means insuperable. Where a high degree 

 of anaerobiosis has been desired, we have found it help- 

 ful to make use of a stream of compressed hydrogen 

 instead of using hydrogen generated in the laboratory. 

 This is followed by the employment of the pyrogallic 

 method for removing the last trace of oxygen. Where 

 a somewhat less high degree of anaerobiosis suffices it 



