1 62 Elements of Water Bacteriology. 



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 

 Houston, 1898, 1899) have shown that the B. sporogenes 

 occurs in English sewage in numbers varying from 30 to 

 2200 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). 



Since this organism is not present in very large num- 

 bers, even in sewage, the test of a water supply must be 

 made with large samples, and the concentration of at least 

 2000 c.c. of water by filtration through a Pasteur filter 

 is recommended by Horrocks as a necessary prelude 

 (Horrocks, 1901). Since the spores of an anasrobic 

 bacillus may persist for an indefinite period" in polluted 

 waters, their presence need not necessarily indicate 

 recent or dangerous pollution. On the whole, it does 

 not appear that the 'practical application of the anaerobic 

 test wiU ever be a wide one. 



Besides the streptococci and the ahaerobic spore formers, 

 various intestinal bacilli, more or less closely allied to the 



