S04 MICROBIOLOGY OP SPECIAL SIGNIFICANCE^ 



B. typhosus. Broth and agar containing brilliant green are now used 

 for this purpose.* The tubercle bacillus when present, may some- 

 times be separated by digesting the faeces in alkaU or in antiformin 

 solution, washing the residue and planting it on Petroff's mediumf 

 or injecting it into guinea-pigs. Entamoeba coli and Entamoeba dys- 

 entericB 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 wiU find it essential to consult the general references below and 



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



Geneeal Methods of Sttidy 



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 duodenum or of upper portions of the small intestine may be withdrawn through the 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 quantity! 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). 



• Krumwiede, Pratt and McWilliams, Joum. Infect. Diseases, 1916, XVIII, p. i. 



t PetrofE, Joum. Exp. Med., 191S, XXI, 38. 



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

 bacteria, see MacNeal, Latzerand Kerr, Joum. Infect. Diseases, 1909, VI, 123; ibid 1909 

 VI, S7I. 



