TUBERCULOSIS. 163 



progress in its development by the process just described, it 

 becomes barely visible to the naked eye. Numerous small 

 lymphoid cells be^in to gather around it and may become so 

 numerous as to obscure the little tubercle and cause a break- 

 ing down or liciuefying of the centre. As the tubercle is thus 

 increased in size or is joined by other similar ones, a mass is 

 formed which is surrounded by fibrous tissue (this fibrous 

 tissue formation being common to animals, but not seen in 

 human tuberculosis). The centre of infection now undergoes 

 the dififerent forms of liquefaction necrosis, followed by case- 

 ation, the depositing of lime salts and calcification, giving us 

 the typical tubercle showing all the stages found in post 

 mortem examination ; namely, caseation, calcification and 

 encapsulation. 



If the efforts of the little, scavenging leucocytes of the 

 blood and lymph vessels are sufficiently strong they may 

 break down and carry away the little tubercle, or build a wall 

 of connective tissue around it and smother it. But if there 

 are too many tubercle bacilli for the action of these little 

 scavengers to destroy, the tubercle breaks out and multiplies, 

 thus reaching the blood and surrounding h-mphatic glands, 

 causing a f^cneralized case of tuberculosis, that may be carried 

 to any part of the bod}^ by means of the circulation. 



Just here I will pause for a moment to say, that as proof 

 of the arresting and overcoming of the disease of tubercu- 

 losis in its incipient stages, we find many of these calcified 

 and encapsulated foci in the post mortem examination of 

 food producing animals, and I am firmly of the belief that it 

 is more often overcome in the human being than is commonly 

 supposed . 



Of the most common media for carrying the tubercle 

 bacilli from animal to animal (or animal to man, for that 

 matter), the milk and feces are regarded the most frequent 

 and menacing. For while everj^ cow affected with the disease 

 does not secrete milk contaminated with the bacilli, there are 

 frequently one or more cows in an infected herd whose milk is 



