CHAPTER XXIX 

 DIAGNOSTIC AGENTS 



Two diagnostic agents in common use will be briefly discussed. 

 They are: 



Tuberculin and Mallein. 



TUBERCULIN 



Tuberculin is the concentrated liquid, usually glycerinated 

 bouillon, on which tubercle bacteria have grown until the products 

 resulting from their multiplication, including the disintegrated bodies 

 of dead tubercle bacteria, have become imparted to the medium in 

 sufficient quantity to inhibit their further development. (Moore.) 



Action. Tuberculin is harmless to healthy animals in the doses 

 necessary for diagnostic purposes and produces no symptoms in 

 these animals. In tuberculous animals it causes a rise of tempera- 

 ture which follows a fairly definite course and usually terminates 

 within 18 to 24 hours after its administration, but sometimes per- 

 sists for a longer period of time. After subcutaneous doses of tuber- 

 culin, the temperature of tuberculous animals usually begins to in- 

 crease in from 6 to 8 hours, giving a steady gradual increase for 

 from 2 to 4 hours, followed by a continuous high elevation for a 

 few hours and then gradually returns to normal. In rare cases the 

 elevation of temperature does not take place until 18 or more hours 

 after the injection. Besides the elevation of temperature, animals 

 sometimes show an " organic reaction " manifested by a nervous chill 

 or muscular tremibling. 



Doses. The dose of tuberculin varies with the concentration 

 used. The average adult dose is 0.25 mil of the concentrated Koch 

 tuberculin but this is made up in various dilutions by different 

 maniifacturers. The dose of that prepared at the New York State 

 Veterinary College at Cornell University is 2 mils, and this should 

 be varied according to the weight of the animal. 



Methods of Use. 



Subcutaneous 



Ophthalmic 



Intradermal. 



Subcutaneous. This consists of injecting tuberculin beneath the 

 skin of the animals and noting the temperature before and after 



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