MICHIGAN ACADEMY OF SCIENCE. 131 



pack method wore followed. Miss Normington attempted to determine the 

 thermal death point of this organism, and found in one trial that it survived 

 a temperature of 120 degrees C. (15 lbs. pressure) in the autoclav for 10 

 minutes, but was evidently destroyed at the same temperature and pressure 

 when heated 20 minutes. These results check with those of Burke of Cali- 

 fornia using known strains. 



These few recently worked out examples make one regard with suspicion 

 the verity of the 4)reviously printed statements concerning the thermal death 

 point of the spores of the B. botulinns group. Thus the conclusion must be 

 drawn that the only method of processing for certain types of canned foods 

 which are not easily penetrated bj' heat and which are liable to contain 

 resistant spores, is by steam under pressure, and that a comparatively long 

 processing period must be used. These suggestions are at present in opposition 

 to government teachings. This phase of the subject has no direct bearing on 

 the problem as it is related to the care and use of silage, except that one 

 young farmer suggested that certain kinds of silage may be treated with boiling 

 water previous to filling the silo. His idea was to moisten the silage and make 

 conditions more anaerobic. This practice might have other desirable results. 



One very important point brought out by Burke is that in determining 

 the thermal death point, a definite time limit cannot be set for the develop- 

 ment of the organism owing to the fact that they have a period of lag 

 depending directly upon the time and temperature of heating. Tlie longest 

 period x)f incubation before growth appeared in culture was 53 days. This 

 strain of B. ioiulinus (X) had been heated for 10 minutes. at 15 pounds pres- 

 sure. I have found this same thing true in determining thermal death points 

 of organisms of this type. This point is very important in canning, as the 

 organisms may not develop immediately, but may show up several months to 

 a year or more after canned. 



The next phase of the suTiject I wish to discuss has to do with the influ- 

 ence of certain chemicals, namely^ salt and acids, on the growth and toxtn 

 production of B. botulmtis. A 10 per cent salt solution is said to destroy the 

 spores of this organism within a week (Kendall: General Pathological and 

 Intestinal Bacteriology), while 5 to 6 per cent salt will prevent multiplication 

 (Herzog: "Disease-Producing Microorganisms). Miss Normington carried 

 out salt concentration experiments under my direction with 19 strains of 

 B. botulimis from different sources, using a dextrose broth having a reaction 

 of -0.5 per cent normal, and employing additions of salt ranging from 1 to 10 

 per cent inclusive. Growth was noted in all concentrations with all strains in 

 practically every case in periods from 27 to 49 days after inoculation. Toxin 

 production was not determined. It seems to be a fact that this organism can 

 multiply readily in a slightly alkaline solution in the presence of salt concen- 

 trations varying from 1 to 10 per cent. We know nothing, however, about the 

 effect of a combination of salt and acids such as would occur naturally in 



