EXPERIMENT STATION REPORTS. 175 



REPORT OF RESEARCH ASSOCIATE G. L. A. RUEHLE 



The work of a popular nature consisted in answering letters of inquiry 

 relative to dairy and creamery hygiene and inspection and analysis of the 

 milk supply of East Lansing. Several minor problems have been studied 

 during the past year as follows : 



I. Examinaidon of a commercial brand of pepsin for the cause of a had odor 

 and flavor. 



On June 15, 1921, we received an inquiry from a commercial house in 

 Detroit asking if we could help them to determine the cause of a musty odor 

 in their pepsin. On June 20 we received the sample, a pepsin powder of 1 

 to 10,000 strength. This had an odor which resembled decomposing animal 

 matter, suggestive of the odor of a packing house. The taste also suggested 

 decomposing animal matter as well as being slightly acid and salty. A 

 microscopical examination revealed bacteria in large numbers, including 

 both long and short rods and diplococci. Starting with a 10 gram sample the 

 material was plated out on lactose agar in dilutions from 1 to 10 to 1 to 1,000. 

 The count four days later was 398,000,000 bacterial colonies per gram. 

 The plate cultures had a sharp ammoniacal odor, pervaded by a putrefying 

 odor similar to if not identical with that of the original pepsin. (A sample of 

 Merck's pepsin of unknowTi age was also examined for comparison. This 

 contained 100 bacterial colonies per gram although a microscopical examina- 

 tion revealed many rod-shaped bacteria.) 



The p!ates were overgrown to such an extent that pure cultures could not 

 be fished satisfactorily, so that loop dilution plates were made of both sam- 

 ples of pepsin and cultures fished from these, as follows: 



Merck A — A large, white, irregular surface colony, consisting of large Gram 

 positive rods, with cylindrical spores, many of which were free. 



Merck B- — A small, nearly round, light greenish-yellow surface colony, con- 

 sisting of small Gram negative rods. No spores observed. 



Merck C — A large, nearly white, irregular, sub-surface colony, consisting 

 of large Gram positive rods with cylindrical spores, some of which were free. 

 Probably the same as Merck A. 



B. A. — A large white, nearly round, raised, pultaceous surface colony, con- 

 sisting of slender Gram positive rods with oval central spores in clostridial 

 sporangia. 



B. B. — A large, round, light greenish-yellow surface colony, consisting of 

 short reds, some Gram negative and some Gram positive; no spores seen. 



B. C. — A small, yellow, lens-shaped, sub-surface colony, consisting of short 

 rods, some Gram positive and some Gram negative. No spores seen. 



B. D. — A large, irregular, nearly white, surface colony. Veil-like with 

 lacy edge, consisting of long, slender rods and filaments, which stained faintly 

 Gram positive. Round terminal or sub-terminal spores, with tags of pro- 

 toplasm on the end of the sporanginum containing the spore. 



These various cultures were inoculated singly and in combinations with 

 each other into sterile beef infusion and allowed to incubate. Only those 

 cultures containing "B. B." had the putrefying odor of the origiiial pepsin 

 so it was concluded that '*B. B." was the responsible organism, 



