l6o WOOLFOLK : 



tracting tuberculosis from animal source regardless of what- 

 ever difference of opinion may exist in the minds of some 

 investigators. It is certainly more reasonable to guard against 

 exposure to infectious material scattered by both persons and 

 animals than only against that scattered by persons. Protec- 

 tive measures that take into account the clearl}' defined 

 menace and neglect the highly probable danger are insufficient, 

 especially where the probable danger is, as in this case, 

 believed to be actual by many men such as I have named, 

 and who are competent to judge. 



Under head of frequency in different food producing ani- 

 mals and source of infection, I will say that the frequency of 

 tuberculosis in domestic animals varies according to species, 

 and also according to the origin of the animals. It is rare in 

 the horse and sheep, but a frequent disease in hogs and almost 

 a regular plague in cattle of a certain locality. The per 

 centage varies according to locality and environment — cattle 

 from I to 45 per cent. ; hogs, .2 to 20 per cent. I will not go 

 into a regular statistical account by States, but will say that 

 from tests made with tuberculin and the number found at 

 time of slaughter to be infected with tuberculosis, the per 

 centage in the Eastern States is very much higher than in the 

 Western, and Pennsylvania stands pretty well up in the list 

 of infection, dairy tests showing 15 to roc per cent. 



As to source and manner of infection, before we enter into 

 the minute description of these, I wish to advert to a little 

 anatomy and physiology, in order that I may better convey 

 my subject. No doubt most of you are perfectly familiar 

 with the circulatory system of the body, particularly the 

 blood, but I will hurriedly run over it to freshen us up. The 

 blood is pumped into the arteries from the left side of the 

 heart, from the arteries into the minute capillaries, there nour- 

 ishing the body, and is again taken up by the capillaries of 

 the veins, which cany the waste material and gases that are 

 the by-products after the different organs or parts composing 

 the bod}' have used up the nourishment and oxygen contained 



