212 ELEMENTS OF WATER BACTERIOLOGY 



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

 smell of butyric acid and is acid in reaction. Under 

 the microscope the whey is found to contain numerous 

 rods, some motile, others motionless." 



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 nitration through a 

 Pasteur filter is recommended by Horrocks as a necessary 

 prelude (Horrocks, 1901). The Committee on Standard 

 Methods of Water Analysis (1912) recommends the 

 following enrichment procedure for the isolation of B. 

 sporogenes which avoids physical concentration. Vari- 

 ous dilutions of the water to be tested are incubated 

 in fermentation tubes containing liver broth for 24 hours 

 at 37. If B. sporogenes is present gas will be evolved 

 and a characteristic " vile odor " will be produced. 

 If this reaction is obtained the contents of each posi- 

 tive tube is transferred to an Erlenmeyer flask or large 

 test-tube and heated at 80 C. for 10 minutes to destroy 

 vegetative cells. One c.c. of broth containing sediment 

 is withdrawn from the bottom of each flask and enriched 

 once more in a fresh liver broth tube. B. sporogenes 

 will now usually be present in pure culture showing 

 large sluggishly motile bacilli containing spores. A 

 gelatin stab culture made from these 24-hour liver broth 

 tubes will show after 48 hours incubation at 20 a dis- 

 tinct liquefying anaerobic growth beginning about 2 

 cm. below the surface with gas bubbles at the top of the 

 liquefied area. In order to obtain absolutely pure 

 cultures it is necessary to fish from liver broth tubes 



