30 



While these two examples show what the action of tuberculin 

 usually is in case of healthy and tuberculous animals, unfortunately 

 the difference is not always so well marked, and with but a slight 

 elevation of the temperature in either healthy or diseased, it some- 

 times becomes impossible to say from the variations whether an 

 animal is the subject of the disease or not. In all instances where 

 there is a decided rise of the temperature after tuberculin has 

 been used, it becomes necessary, in order to make a diagnosis of 

 tuberculosis, to exclude all other possible causes of a rise, — such 

 as acute inflammation in any part of the body, excitement, exces- 

 sive heat, etc. For this reason tuberculin is most valuable in the 

 hands of those who are thoroughly conversant with the various 

 diseases of cattle. 



The use of tuberculin does not give any information as to the 

 extent of the development or the rapidity of the progress of tuber- 

 culosis in cattle. It has been found that the reaction is fully as 

 great in those animals in which there are but one or two small 

 inert tuberculous nodules no larger than a buck shot as it is when 

 there are extensive and active lesions. Consequently, in order to 

 prove the accuracy of the tuberculin test, it becomes necessary to 

 make a thorough examination in all autopsies, to detect the 

 minutest nodules that may be present. In many cases this re- 

 quires prolonged search and a knowledge of the gross and micro- 

 scopical appearances of tuberculous tissue. 



Following there appear the conclusions drawn from a series O- 

 experiments made with tuberculin at the Massachusetts Agricult- 

 ural College. These are taken from Bulletin No. 27 of the Hatch 

 Experiment Station, a few copies of which are still in the hands of 

 the director for distribution. 



1. That it is unsafe to purchase animals to add to a healthy 

 herd from a herd in which tuberculosis has existed. 



2. That poor sanitary surroundings, especially imperfect ven- 

 tilation and insufficient light, are favorable to the rapid spread of 

 tuberculosis among cattle. 



3. That it is much better to dispose of excrement outside of 

 stables than in cellars underneath them. 



4. That mangel's and other stable fixtures which increase the 

 amount of surface, cracks and corners that cannot be easily 

 cleaned are objectionable, from the fact that when the germs of 

 tuberculosis become scattered, under such conditions they are not 

 easily destroyed by the use of disinfecting fluids. 



5. That infected stables bear close relation to the propagation 

 of the disease. 



