88 



Scientific Proceedings (32). 



water, a definite cryoscopic depression. In harmony with deduc- 

 tions from titration- and conductivity-data' the results are such as 

 indicate that casein behaves towards bases, essentially as a mono- 

 basic acid possessing a molecular weight, in solutions neutral to 

 litmus, of approximately 2,000. 



41 (379) 



The daily excretion of bacteria in the feces of healthy men. 



By W. J. MACNEAL, LENORE L. LATZER and 

 JOSEPHINE E. KERR. 



\^From the Laborato)y of Physiological Chemistry, Department of 

 Animal Husbandry, University of Illinois, Urbana, Ill.'\ 



During the past year we have examined at intervals of about 

 two weeks the fecal bacteria of each individual in a group of twelve 

 men who were the subjects of a prolonged metabolism experiment. 

 These men were fed a mixed diet, in quantity according to their 

 choice at the beginning of the experiment. Altogether we have 

 examined bacteriologically 266 stools. 



The quantity of bacteria in each of these stools was estimated by 

 two different methods of microscopic counting and in about half of 

 them the quantity of bacterial dry substance was also estimated by 

 the gravimetric method of Strasburger. 



In the individual examinations the largest number of bacteria 

 observed was 816 x 10' bacterial cells per gram fresh feces, 

 2,642 X 10® bacterial cells per gram dry feces. The smallest 

 number of bacteria counted was 124 x 10' per gram fresh feces, 

 983 X 10^ per gram dry feces. By the gravimetric method the 

 largest quantity of bacterial dry substance observed was 42.53 per 

 cent, of the fecal dry substance or 13.2 per cent, of the moist 

 feces. The smallest quantity of bacterial dry substance obsei-ved 

 was 14.03 per cent, of the fecal dry substance or 2.6 per cent, of the 

 moist feces. The average of all examinations was 375 x 10^ bac- 

 terial cells per gram fresh feces; 1,587 x 10^ bacterial cells per 

 gram dry feces ; bacterial dry substance in fecal dry substance, 



T. Brailsford Robertson: Journ. of Physical Chein., 1908, xii, 479, etc. 



