io8 MILK AND THE PUBLIC HEALTH chap. 



it within three days, gives no neutral red reaction, pro- 

 duces acid in lactose and saccharose media, never in mannite, 

 and not usually in salicin, raffinose, or inulin. It is non- 

 pathogenic to mice. It is of considerable significance that in 

 several other cases quite different streptococci were isolated. 



In view of the possible relationship of mastitis in cows to 

 human disease it is a matter of great importance to consider 

 how far the causal organisms of mastitis are present in 

 quarters which clinically appear quite unaffected. To in- 

 vestigate this question, the milk of all four quarters was, 

 as far as possible, examined in every case. Excluding cases in 

 which all four quarters were attacked, in 84 per cent of the 

 cases due to streptococci identical organisms were isolated in 

 one or more of the healthy quarters. In some instances they 

 were present in only one healthy quarter, in others in all of 

 them. It should be noted that not only were these strepto- 

 cocci found in quarters which appeared sound when examined 

 by a veterinary surgeon, but in quarters which frequently 

 showed no evidence of any inflammatory reaction, as demon- 

 strated by the extremely sensitive cytological examination. 

 The milk appeared to be perfectly healthy to the naked eye. 

 Although these streptococci (identical with those in the affected 

 quarters) were present, usually the healthy quarters did not 

 become subsequently involved. 



From a public health point of view these results are of 

 considerable significance. In cases of mastitis in cows it is a 

 quite common practice to use the milk from the seemingly 

 unaffected quarters, although the secretion of the diseased 

 quarters is recognised as unfit. The results obtained show 

 that in most cases the farmer is thus adding to the vended 

 milk very large numbers of streptococci indistinguishable from 

 those causing the mastitis. 



The primary problem from the human standpoint is whether 

 the streptococci found in cow mastitis are pathogenic to man. 

 To elucidate this further investigation was required. Extended 

 comparison was therefore instituted between the streptococci 

 found in these two conditions. The streptococci found in 

 16 cases of human sore throat were carefully investigated. 

 Two chief types were found, confirming the results previously 

 found by Andrewes and Horder. The most prevalent type 



