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herds requires that we should ]iave some knowledge on the following, 
special subjects, which will be discussed in order: The character of 
tuberculosis as a disease of cattle; the manner in which tubercle 
bacilli are expelled by tuberculous cattle ; the general appearance of 
tuberculous cattle that expel tubercle bacilli; how tubercle bacilli 
from cattle get into milk and other dairy products ; the virulence and 
vitality of tubercle bacilli in dairy products ; the proportion of tuber- 
culous cows among those in use for dairy purposes; and, finally, the 
frequency with which dairy products have been proven under existing 
conditions to contain tubercle bacilli. 
THE CHARACTER OF TUBERCULOSIS AS A DISEASE OF CATTLE. 
Tuberculosis of cattle, as of j)ersons, may be acute and rapidly 
progressive and run its course quickly from infection to death. This 
is rare. As a rule, it is insidious, chronic, and slowly progressive, and 
the bodies of its victims are able to adapt or adjust themselves to 
the gradually increasing, destructive changes it causes until quite 
extensive harm has been done or vitally important organs have be- 
come seriously involved. The result is that the disease may be pres- 
ent in the body a long time without external manifestations of its 
existence. It may attack any part of the body singly and remain 
confined to it or it may attack several or many parts simultaneously 
or successively. Its favorite location in the bodies of cattle, as in 
those of persons, is the lung. 
The tuberculous lungs of cattle do not show the decided cavity 
formation seen in human tuberculous lungs, but cavities in direct 
communication with the exterior of the body through bronchial tubes, 
more or less completely surrounded by heavy, dense, connective- 
tissue walls, are common. The dissimilarity of the lesions in the 
lungs of persons and cattle are no doubt the result of normal, anatom- 
ical difierencek The lungs of cattle, unlike those of persons, have 
very decidedly outlined lobules, which are separated from each other 
by webs of loose, elastic, connective tissue. This tissue is so abundant 
that it admits of a serous and cellular infiltration through which 
the lobules may be separated from each other as much as a sixteenth 
or even an eighth of an inch, and consequently not only pulmonary 
tuberculosis, but most lung diseases of cattle and other ruminants, 
have a special, distinct character. 
Tuberculosis is more effectually concealed in the bodies of cattle 
than in those of persons, and we all know how long a diagnosis with 
persons may remain in doubt. Perception, or the faculty of receiv- 
ing impressions, is keenest where the nervous s^^stem has the highest 
development. Persons, though their perception of pain is much 
keener than that of lower animals, complain little during the earlier 
