OTHER INTESTINAL BACTERIA 107 



the tube. When the tube is opened, the whey has a smell 

 of butyric acid and is acid in reaction. Under the micro- 

 scope the whey is found to contain numerous rods, some 

 motile, others motionless." 



The B. sporogenes when isolated in pure culture on 

 glucose agar is a stout rod. It liquefies gelatin, forming 

 in this medium large oval spores. It is strongly patho- 

 genic for guinea-pigs, by which character it is distinguished 

 from the B. butyricus of Botkin. 



The researches of Klein and Houston (Klein and Hous- 

 ton, 1898, 1899) have shown that the B. sporogenes occurs 

 in English sewage in numbers varying from 30 to 2000 per 

 c.c. and that it is often absent in considerable volumes of 

 pure water. In Boston sewage it may usually be isolated 

 from .01 or .001 of a c.c. (Winslow and Belcher, 1904). 



Evidently in order to have any significance, an exam- 

 ination for this organism must be made with large samples 

 and the concentration of at least 2000 c.c. of water through 

 a Pasteur filter is recommended by Horrocks as a neces- 

 sary prelude (Horrocks, 1901). Since the spores of an 

 anaerobic bacillus may persist for an indefinite period in 

 polluted waters, their presence need not necessarily indi- 

 cate recent or dangerous pollution. Since the number 

 present even in sewage is so small and so variable, no 

 quantitative standard can be established; on the whole, 

 it does not appear that the practical application of the 

 anaerobic test will ever be a wide one. 



There are numerous other sewage bacteria whose 

 presence is more or less constantly characteristic of pol- 



