BACTERIA IN THE INDUSTRIES 1 97 



render them invisible or unrecognizable under the compound microscope. 

 The microscope will therefore reveal all of the microorganisms, and also 

 other contaminations, which were introduced or which developed in the 

 milk prior to and up to the very moment of the final processing. 



The following findings and recommendations pertain to evaporated 

 milks, whole and skimmed, sweetened and unsweetened : 



1. The organisms most commonly present are 



a. Cocci, 



b. Diplococci, 



c. Diplobacilli, 



d. Streptococci, 



e. Bacilli, 



f. Tetracocci (Sarcina), 



naming them in the order of their relative abundance. Of these groups, 

 the diplococcus, diplobacillus, and streptococcus forms are the most im- 

 portant from the viewpoint of the food bacteriologist. 



2. Many of the coccus and diplococcus forms are no doubt derived 

 from the streptococcus forms. Because of the fact that coccus forms may 

 be confused with minute fat globules and nonbacterial organic particles 

 of spherical form, it is suggested that the coccus count be omitted. 



3. The diplobacillus forms thus far observed are readily confused 

 with diplococcus forms, because the individual cells are but slightly 

 elongated, the two diameters being as i : 1.3. It is therefore recom- 

 mended that the diplococcus and diplobacillus forms be included in one 

 and the same count. 



4. Bacilli are, as a rule, sparingly and irregularly present in evaporated 

 milks. The same may be said of the tetracoccus forms. 



5. It does not appear practicable to make body cell counts of evapo- 

 rated milks, and it is recommended that this be omitted as a laboratory 

 routine. 



6. The amount of organic debris present in evaporated milk is quite 

 variable in different cans of a given brand of canned milk. It is, however, 

 recommended that milk be examined as to the relative amount of organic 

 debris present, bearing in mind that the careless or inexperienced micro- 

 analyst may confuse casein particles, agglutinated butter fat globules 

 and lactose crystals, with organic debris. 



7. Organoleptic testing is of considerable importance in milk examina- 

 tion. Consistency, color, odor, and taste, should be carefully noted. 



8. It is also self-evident that the presumptive colon bacillus test should 

 give negative results with all heat-sterilized milks. 1 



1 It is a notable fact that pasteurization does not always kill the colon bacilli in milk. 

 Numerous samples of pasteurized milk have been found which subsequently contained 

 practically pure cultures of the colon bacillus. 



