No. 4.] CATTLE COMMISSIONERS' REPORT. 231 



of great value in connection with the diagnosis. The cough in the 

 earlier stages is a dry one, occurs in paroxysms, and is due to an 

 irritation of the lining membrane of the bronchial tubes, which is 

 often one of the first effects of the tubercular poison. Because of 

 this peculiarly irritable condition the respiratory tubes are quite 

 susceptible to slight changes of atmosphere ; therefore when a cow 

 of this sort is moved from a warm place to a cold one, or vice versa, 

 she is much more apt to cough than not ; as she is, for the same 

 reason, when made to take exertion of almost any sort in a suffi- 

 cient degree to cause the slightest increase in the respiratory effort. 

 In the later stages the cough becomes moist because it depends 

 upon the existence of a real bronchitis of greater or less extent. 

 If this bronchitis is extensive the cough will be frequent, distress- 

 ing, and will take place after the slightest exertion or, at intervals, 

 without exertion. It must be remembered, however, that unless 

 there is irritation or inflammation of the respiratory tube, with the 

 tuberculosis, there will be no cough ; and while there are a great 

 many cases of tuberculosis in cows that do not cough at all attract- 

 ively, there are also many cows that do cough considerably that 

 have no tuberculosis. Cows are like men in that they cough from 

 many causes quite aside from tuberculosis ; and if the cough 

 comes from irritation of the same parts of the tubes, to the same 

 extent, from any cause, it will have about the same sound and 

 occur under the same circumstances. 



Changes, caused by the Disease, found after Death. 



As has been said, it is now an accepted fact that by the terra 

 tuberculosis is meant a diseased condition brought about by the 

 entrance of a specific germ into the body of a susceptible living 

 animal. This germ is technically called a tubercle-bacillus and can 

 be seen with a high-power microscope. 



Tubercle-bacilli having gained entrance may be carried to various 

 parts of the body by the circulating blood ; by the cii'culatiou in 

 the lymphatic system ; by building upon themselves, as when they 

 have gained previous lodgment on the surface of a membrane ; or 

 by transplantation, as when phlegm from a diseased portion of 

 lung is coughed up, and before being expectorated falls into an- 

 other portion of lung, or is swallowed. 



Tuberculosis may be local or general ; local, when it is limited 

 to the organ or tissue that was first invaded, and which it grad- 

 ually but ultimately destroys ; general, when large numbers of the 

 bacilli have gained simultaneous lodgment, by having been widely 

 scattered by the blood current, and have then, by being upon 

 soil peculiarly adapted to their growth, sprung up in large 

 numbers. 



