farmers' institutes. 269 



The germ causing tuberculosis is very much smaller than either the 

 loose cells floating in the body, or the fixed cells constituting the tissues, 

 and when once it has found entrance into an animal body it can pene- 

 trate between the tissue cells. This little germ, the bacillus tuberculosis, 

 finds its way into the animal body through various channels, and is able 

 to make use of the tissues in which it becomes lodged, as food for growth 

 and multiplication in numbers. Strange as it may seem, this germ is 

 able to grow in any tissue of the animal body, hence it sets up diseased 

 processes in the lungs, liver, glands, muscles, skin, and even the bones. 

 The development of the germs in any tissue produces an irritation at 

 that point and the tissue undertakes to protect itself from further en- 

 croachment by building a wall round about the invaders. Loose cells 

 accumulate in an effort to surround the disease germs causing a thicken- 

 ing of the tissues and a heaping up as it w-ere into a little hillock or nodule. 

 Such a nodule is spoken of as a tubercle, hence this disease is called tuber- 

 culosis. The colony of germs within the tubercle secrete a poisonous 

 substance which causes the death of the layers of cells next to them and 

 while the tubercle is continuously strengthened on the outside it is de- 

 stroyed on the inner side. The dead elements of the enclosing wall are 

 converted into a cheesy mass having a white or yellowish white color, 

 while the outer surface of the tubercle may be either gray or pink in 

 color, depending somewhat on the place in which it develops. These 

 tubercles var>- in size from a pin head to a pea, and when growing upon 

 a serous membrane they have a gray or pearly color and constitute the 

 old time "pearl disease" of cattle. These tubercles may grow close to- 

 gether and accumulate in masses as large as a walnut, a man's fist, or even 

 larger than this. When the disease process has developed slowly the 

 cheesy centers of the tubercjes contain gritty particles of lime salts. 

 Sometimes they coalesce, run together and the dead cells become one 

 large cheesy mass. 



If you are examining the carcass of a cow and should find tubercles 

 such as have been described, and by cutting them open you find the cen- 

 ters are made up of cheesy, gritty masses, you will know that they are 

 the lesions of tuberculosis. The parts of the body in which these tuber- 

 cles are found are rarely the seats of other diseases producing like lesions, 

 hence there is little chance of being mistaken. 



Tuberculosis spreads among dairy cattle quite slowly when they are 

 not housed, but when stabled and fed from a common manger, the dis- 

 charges from the lungs, coughed out by a cow on the hay, manger or 

 floor, are swallowed with the food by the cows in the stanchions next to 

 the afflicted one, or those down the line in the direction in which the hay 

 is pushed along the manger. A calf suckling a tuberculous cow is quite 



