146 ANNUAL REPORT OF THE Off. Doc. 



healthy offspring at birth, but may impart to her progeny what is 

 termed a tubercular diathesis or an hereditary predisposition to 

 contract tuberculosis if exposed to the infection. 



There are other predisposing conditions of body and environment 

 which contribute to the development of this disease. 



A weakened physical condition due to insufficient or improper 

 food, insanitary housing, unusual exposure to inclement weather 

 and the drain on the system of dairy cows caused by heavy produc- 

 tion of milk, will undoubtedly cause lessened resistance and assist 

 in the development of the disease after infection occurs. 



A damp, crowded stable with insufficient light and ventilation, 

 will prove a veritable hot-bed for the propagation of tuberculosis. 



While it is apt to be found in virulent form in sucli a place, it is 

 also found to a lessened degree in properly constructed and well 

 kept barns, due to failure to take proper precautions against the 

 introduction of the infection. 



There are no positive characteristic physical or clinical symptoms 

 of tuberculosis in the living animal. Any symptoms shown by a 

 tuberculous animal may be exhibited by other diseases or caused by 

 some derangement of physiological functions. For this reason diag- 

 nosis by physical examination is uncertain except in advanced cases. 

 The onset of the disease is always unobtrusive and it usually pro- 

 gresses so slowly that no hint of its presence is given until some 

 vital organ has become seriously affected. An animal may be in- 

 fected in very early life and the disease remain latent until maturity. 

 During this time the presence of the disease cannot be determined 

 except by use of the tuberculin test. Any organ, or any set of or- 

 gans may be attacked by tuberculosis; consequently in a considera- 

 tion of suggestive symiitoms, we must have regard for the normal 

 functions of various organs in order to note physical changes which 

 may be the result of impaired function. 



An exaggerated importance is usually attached to the presence or 

 absence of a cough in a suspected animal. In many instances, farm- 

 ers will not entertain the idea that a cow may have tuberculosis 

 unless there is a noticeable and persistent cough. On the other hand 

 they will have grave suspicions of any cow which exhibits such a 

 symptom. When we consider the numerous causes from which a 

 cough may arise, the fallacy of accepting this as a constant or char- 

 acteristic symptom is apparent. Coughing as a symptom of tubercu- 

 losis is only exhibited when the lungs or some other portions of the 

 respiratory apparatus are effected. Even then it is not the loud, 

 deep and frequent cough, which the layman naturally expects to 

 hear, but rather subdued or repressed and infrequent; except in the 

 later, advanced stages of the disease, when the animal may be racked 

 by violent and conlinuons spells of coughing. A tuberculous cough 

 is more apt to be noticed in the morning when the stable is first 

 opened or when the animal is forced to exercise. Cows do not usu- 

 ally appear to cough up anything, but it will be noticed after cough- 

 ing that they swallow, which indicates that some material has been 

 raised from the lungs or air passages into the throat or mouth. 

 While cows do not usually eject any coughed up material, many 

 tuberculosis germs may escape from the mouth with the saliva in a 

 fine spraj' or be discharged from the nostrils. 



