DISEASES COMMUNICABLE IN MILK 33 



miliary tuberculosis or galloping consumption the progress of which is 

 very rapid. Sometimes the serous membranes covering the lungs or 

 intestines become seeded with these grains giving rise to a condition 

 known as " pearl disease." Neither the rate of progress of tuberculosis 

 nor the time the sickness will last can be predicted; these depend upon the 

 stamina of the host, the virility of the bacteria, the massiveness of the 

 original infection, and other factors imperfectly understood. 



So long as the disease is confined to bones, glands and other structures 

 that do not communicate with channels leading to the exterior of the 

 animal, it is said to be closed and the animal is regarded as being 

 unable to infect others, but when structures such as the lungs, liver, 

 gall-bladder, kidneys, urinary bladder, udder, and genital organs, that 

 do lead without the animal, are invaded the creature becomes a highly 

 dangerous source of contagion to susceptible beasts and to man, for under 

 such conditions living germs are scattered broadcast. In this state the 

 animal may reinfect itself, as for instance, by inhaling sputum that is 

 raised but not coughed out, thus establishing new diseased foci in the 

 lungs or by swallowing such sputum it may set up infection in the viscera 

 or other parts of the body. 



Entrance of Tuberculosis Germs into the Body. Tuberculosis germs 

 gain entrance to the body in two principal ways: by being breathed in 

 and by being swallowed with food. There is dispute as to which of these 

 modes of infection is the commoner; that neither is infrequent seems 

 probable. 



Passage of Tuberculosis Germs from the Body. The germs of tuber- 

 culosis are expelled from the body in the sputum, the urine and feces, 

 and in discharges from the genital organs. The sputum is infectious 

 when the lungs are diseased and so the droolings and the fine spray that 

 is ejected when the animal coughs spread the disease. Thus the sick 

 cow may lick herself and other cows or may "nose" them and so distrib- 

 ute the germs. Coughing is likely to spread contagion to other animals 

 especially to those confined in adjoining stalls. In fact the pestilence 

 is scattered wherever the infected sputum falls, in the feed, mangers, 

 salt boxes, watering troughs, on floors and in pastures. Tubercle bac- 

 teria are expelled in the urine when the kidneys or urinary bladder are 

 diseased, and by these discharges the flanks of the animals and the ground 

 are infected. The feces are infected when the animal has intestinal 

 ulcers, when the liver or gall-bladder is diseased, or the lungs are so that 

 infected sputum swallowed by the animal is passed. On some farms 

 manure is piled where cows can get at it and mouth it and thus infect 

 themselves. Manure from a tuberculous animal may infect whatever 

 it touches including the exterior of the animal itself. So the hair and 

 dirt that falls from such a creature into the milk infects it; consequently 

 a cow without tuberculosis of the udder may infect milk. 



