RELATION OF MICROORGANISMS TO SOME SPECIAL DAIRY PRODUCTS. 373 



bacterial growth in material which is held below the freezing temperature. 

 This, however, did not seem to be the case in samples examined by the 

 investigators already mentioned. They found in samples held about a 

 month that there was normally a decrease in the bacterial count and 

 also in the amount of gas production for a number of days, after which 

 there was frequently a marked increase in the bacterial counts. These 

 results would seem to indicate that even in the frozen condition there 

 may be some increase in the number of bacteria present. The number 

 of these experiments, however, is not sufficient to justify very general 

 conclusions. The work of Conn and Esten* in holding milk at i may 

 throw some light upon this question. 



If the cream from which the ice cream is made has been produced and 

 handled under sanitary conditions, the bacterial content should consist 

 chiefly of organisms of the Bad. lactis acidi type, in which case the high 

 count in the ice cream might not be objectionable. If, on the other hand, 

 the cream has been held in cold storage for some time under conditions 

 which inhibit the growth of the lactic organisms and permit the develop- 

 ment of putrefactive types, bacterial poisons may be developed in the 

 cream, which will be highly objectionable. There seems to be little 

 doubt that this is the cause of the cases of ptomain poisoning, resulting 

 from the use of ice cream. It is known that certain types of bacteria, 

 especially those belonging to the so-called putrefactive group, are capable 

 of developing at very low temperatures and can, therefore, produce con- 

 siderable quantities of toxic products in the cream. Whether or not 

 these products are developed before the cream is manufactured or whether 

 they may develop in the frozen product cannot at present be stated. In 

 general it can be said that the total bacterial count does not indicate the 

 wholesomeness of the ice cream any more than does a similar count in 

 buttermilk or in thf commercial fermented-milk drinks. The kinds of 

 organisms present is a far more important question from the standpoint 

 of the wholesomeness of the ice cream. 



* Annual Report, Storr's Experiment Station, 1901. 



