MICROORGANISMS OF THE DIGESTIVE TRACT 6oi 



B. typhosus. Broth and agar containing brilliant green, agar containing 

 fuchsin and sulphite (Endo's medium) and agar colored with eosin and 

 methylene blue are employed for this purpose. The tubercle bacillus 

 when present, may sometimes be separated by digesting the faeces in 

 alkali or in antiformin solution, washing the residue and planting it on 

 Petroff's medium* or injecting it into guinea-pigs. Entamceba coli and 

 Entamcela dy sentence should be searched for with the microscope in 

 fresh warm faeces obtained after a dose of salts. 



This brief mention of a few procedures indicates the specialized 

 character of the microbiological technic in this field. The laboratory 

 worker will find it essential to consult the general references below and 

 to study carefully the original papers bearing upon his field of work. 



GENERAL METHODS OF STUDY 



COLLECTION OF MATERIAL. Material for microbiological study may be ob- 

 tained from the mouth, fauces or pharynx by means of a sterile cotton swab, by the 

 ordinary platinum loop or other instrument suitable for the special purpose in view. 

 This material should be examined promptly, or, if this is impossible, it should 

 at once be spread upon slides for subsequent microscopic study and, if cultures are 

 to be made, it should be suspended in sterile salt solution, or better in sterile ascitic 

 fluid, and refrigerated until the proper media can be inoculated. From the stomach, 

 fluid may be readily obtained through a stomach tube and the contents of the 

 duodenum or of upper portions of the small intestine may be withdrawn through the 

 slender duodenal tube of Einhorn. The contents of the lower part of the small 

 intestine and the upper part of the large intestine can be readily obtained only at 

 surgical operations upon the intestine, at autopsies or from individuals in whom an 

 intestinal fistula has been established. The contents of the lower part of the large 

 intestine are best collected by means of a special glass instrument in the case of 

 young children. In older children and adults a natural stool or one obtained 

 after salts or other cathartic may be utilized. 



In every instance, contamination of the material with extraneous organisms is 

 to be strictly avoided by careful sterilization of implements and receptacles and 

 any alteration of the specimen after collection must be reduced to the minimum 

 by examining it promptly, although, for some purposes the use of refrigerated speci- 

 mens may be permitted. 



The quantityf of microbic cells present may be ascertained by numerical count 

 of those present in an accurately measured portion of the material, or if they are 

 very abundant they may be physically separated out from a weighed portion 

 by fractional sedimentation in the centrifuge, after which they are dried and weighed 

 (method of Strasburger). 



* Petroff, Journ. Exp. Med., 1915, XXI, 38. 



t For detailed directions concerning quantitative methods as applied to the study of faeca 

 bacteria, see MacNeal, Latzer and Kerr. Journ. Infect. Diseases, 1909, VI, 123; ibid., 1909, 

 VI, S7I. 



