BACTERIOLOGY OF MILK IX ITS RELATION TO DISEASE -4:,:, 



to show common characteristics, contained, besides the predominating 

 colon types, other organisms which differed widely in different spe< -i - 

 and in different localities. Cleanliness in handling the milk and the 

 temperature at which it had been kept were also found to have a 

 marked influence on the predominant varieties of bacteria present. 



Pathogenic Properties of the Bacteria Isolated. Intraperitoneal injec- 

 tion of 2 c.c. of broth or milk cultures of about 40 per cent, of the varieties 

 tested caused death. Cultures of most of the remainder produced no 

 apparent deleterious effects even when injected in larger amounts. 

 The filtrates of broth cultures of a number of varieties were tested, 

 but only one was obtained in which poisonous products were abun- 

 dantly present. Death in guinea-pigs weighing 300 grams followed 

 within fifteen minutes after an injection of 2 c.c.; 1 c.c. had little effect. 



As bacteria in milk are swallowed and not injected under the skin, 

 it seemed wise to test the effect of feeding them to every young animals. 

 We therefore fed forty-eight-hour cultures of 139 varieties of bacteria 

 to kittens of two to ten days of age by means of a glass tube. The 

 kittens received 5 to 10 c.c. daily for from three to seven days. Only 

 one culture produced illness or death. A full report on the identifica- 

 tion of the varieties of bacteria met with in this investigation can be 

 found in an article by Dr. Letchworth Smith in the 1902 Annual 

 Report of the Department of Health. 



After three years of effort to discover some relation between special 

 varieties of bacteria found in milk and the health of children the con- 

 clusion has been reached that neither through animal tests nor the 

 isolation from the milk of sick infants have we been able to establish 

 such a relation. Pasteurized or "sterilized" milk is rarely kept in 

 New York longer than thirty-six hours, so that varieties of bacteria 

 which after long standing develop in such milk did not enter into our 

 problem. The harmlessness of cultures given to healthy young kittens 

 does not of course prove that they would be equally harmless in infants. 

 Even if harmless in robust infants, they might be injurious when sum- 

 mer heat and previous disease had lowered the resistance and the 

 digestive power of the subjects. In a recent investigation by Dr. D. H. 

 Bergey some connection between diarrhoea and pus and streptococci 

 were found. 



The results of this investigation appear to warrant the following 

 conclusions : 



1 . The occurrence of pus in cows' milk is probably always associated 

 with the presence in the udder of some inflammatory reaction brought 

 about by the presence of some of the ordinary pyogenic bacteria, espe- 

 cially of streptococci. 



2. When a cow's udder has once become infected with the pvnirenic 

 bacteria the disease tends to persist for a long time, probably extending 

 over several periods of lactation. 



3. Lactation has no causative influence per se upon the cellular and 

 bacterial content of cows' milk, though it probably tends toward the 

 aggravation of the disease when the udder is once infected. 



