70 MILK HYGIENE 



when the milk in which the defect was discovered was 

 drawn. 



IV. TRANSMISSION OF INFECTION BY MILK 

 FROM CATTLE TO MAN 



A series of specific diseases are common to cattle and 

 man, and the pyogenic bacteria of man occur in different 

 diseases of cattle. Therefore, the question is pertinent : 

 Can milk, before it is drawn, contain bacteria that are 

 pathogenic for man! It is quite natural that this may 

 occur when the disease affects the udder ; but how is it 

 with diseases without this local manifestation? Differ- 

 ent answers have been given; some investigators affirm 

 that such an excretion of bacteria regularly takes place 

 through the udder; others (Jensen, Gartner, etc.) insist 

 that this is not the case, that such excretion is gen- 

 erally limited to cases in which, during the course of the 

 disease, local changes appear in the udder tissue (hem- 

 orrhage, inflammation), and that anthrax bacilli, for 

 example, by no means always pass from the blood to the 

 milk of the infected cow. An exceptional condition 

 occurs in foot-and-mouth disease, as in this malady the 

 milk contains much infectious matter. But it will be 

 shown later that the milk from cows with this disease 

 shows a decided departure from the normal, so that it is 

 probable that here, too, the excretion of infectious mate- 

 rial is associated with pathological change in the udder 

 tissue. 



In the case of certain diseases of cows, it may occur 

 that pathogenic micro-organisms become mixed with the 

 milk during milking and, from a practical standpoint, 

 this has, in effect, the same significance as an excretion 

 through the udder. 



A more minute account of the diseases of cattle 

 which may cause a direct contamination of milk with 

 pathogenic microbes will be given below. 



