DIRECT EXAMINATION 



55 



processes are left to nature the result is not by any means uniform 

 and we have products which are often so vitiated by the develop- 

 ment of undesirable associated organisms as to make the food unfit 

 for use. There is a definite biological relationship between those 

 organisms which initiate desirable fermentations and those which 

 are objectionable ; both kinds are generally present, but fortunately 



Fig. 15. — Vinegar eels from decomposed blackberry pulp. The small particles 

 scattered through the field are yeast cells. Bacteria were also present but they do 

 not show in the illustration. — -{Howard, Yearbook U. S. Dept. of Agriculture, 191 1.) 



the desirable or beneficent forms overgrow the objectionable 

 forms very rapidly, but not always. It should be one of the prin- 

 cipal efforts of the food and drugs bacteriologist to isolate and 

 identify the organisms which are desirable in the production of 

 fermented food products and those which are unquestionably 

 undesirable and objectionable, for in these products it is not a 

 question so much of quantity as of quality of the organisms present. 



