SPONTANEOUS CHANGES IN MILK 125 



bits (in order to test it for tubercle bacilli) Friis discov- 

 ered that 15 of the 28 samples contained bacteria which 

 caused either peritonitis or abscesses or pyaemia. 

 Guinea pigs were generally useless for his experiments 

 because they all died of peritonitis. Similar results have 

 been obtained by many others. 



The forms of bacteria considered in this connection 

 are chiefly streptococci, staphylococci and members of 

 the colon group, some of which are generally present, 

 although, perhaps, in quite small amounts, in market 

 milk; besides these, there are still many other kinds, 

 some of them occurring regularly, in small numbers, and 

 some are only met with now and then. Where do these 

 bacteria come from? Primarily from the dirt that gets 

 into the milk when it is drawn, it is a well-known fact 

 that the excrement contains numerous, and sometimes 

 pathogenic, bacteria. They may also come from cases 

 of mastitis and metritis in the stable; moreover these 

 forms of bacteria are widespread and probably they 

 very often occur in cow stables, as is shown by the fre- 

 quent occurrence of calf cholera. " Calf cholera " is a 

 common name for a group of fatal diseases of new-born 

 calves among which the most usual forms are navel 

 infection (most frequently caused by streptococci, colon 

 bacilli and pseudo-colon bacilli) and diarrhrea or dysen- 

 tery of calves (in most cases caused by colon bacilli). 



It does not follow that all milk containing strepto- 

 cocci or the other bacteria referred to above is harmful 

 or dangerous. But if these are present in large num- 

 bers, they make the milk suspicious and there are many 

 evidences that such milk has been most injurious. It is 

 highly probable that a very great part of the gastro- 

 enteritis, so harmful to small children, is traceable di- 

 rectly to these bacteria. The fact that the mortality 

 among small children in general has decreased to a great 



