SIGNIFICANCE OK RESULTS. 133 



The study of the subject has proceeded in the wrong order. 

 The abnormal has been studied, tests devised and standards 

 set, all from that standpoint. The use of checks to prove the 

 value of tests has been too frequently disregarded. For in- 

 stance, tests have been advocated as of value in detecting the 

 location of diseased animals, without evidence being brought 

 forward to show that the test has been tried on a group of 

 animals known to be diseased. The detection of diseased ani- 

 mals in the herds supplying condemned milk has been accepted 

 as confirmation of the value of a test. 



The work has resulted in directing attention to the normal, 

 which has often been too little considered. At present, the 

 matter is in that period of development in which the fairness 

 of standards and the accuracy of tests are being scrutinized. 

 In judging the merits of the various tests, a number of facts 

 concerning the normal must be considered. 



Streptococci in milk Examination of samples of market milk 

 will show streptococci in a very large percentage of the cases 

 (13, 14, 15, 16, 19). Heinemann has asserted that "Bacillus 

 acidi lactici is a myth," and that the common organism sour- 

 ing milk should be called Streptococcus lacticus. 



Reference has already been made in Chap. I to the fact that 

 an apparently healthy cow was found to harbor a pathogenic 

 streptococcus in the udder for a considerable period of time. 

 In consequence the animal might well be called a streptococ- 

 cus carrier (21). 



There are no generally accepted methods for differentiating 

 the various species of the genus streptococcus found in milk. 

 It cannot at present be determined whether a given strepto- 

 coccus is of human or animal origin, virulent or not, or whether 

 it is a saprophyte. Hemolysis and agglutination have both 

 failed to yield conclusive results (12) . This group has been the 

 despair of the systematists. Winslow and Winslow (33) give 

 a valuable chapter upon streptococci. 



Least of all, is it possible to make a differentiation on mor- 

 phological grounds alone. Our ideas of the hygienic signifi- 

 cance of the presence of streptococci, based on their rare 

 discovery by certain tests, must be revised. 



