PRINCIPLES OF VETERINARY SURGERY 139 



injection is made preferably at ten P. M. and at six A. M. the 

 final observations begin. Temperatures are taken every 

 two hours during the next sixteen hours. A gradual rise to 

 a certain point, no less than two degrees above the highest 

 preliminary temperature, followed by a gradual fall, is the 

 typical reaction. Sudden elevations are of no significance, 

 owing to the many external influences that may temporarily 

 disturb the temperature of an excitable bovine. 



As in the case of glanders, the tuberculin test is valued 

 highest by those having the most experience, and is quite 

 universally condemned by the careless and inexperienced as 

 being unreliable and even harmful. 



Tuberculin. — The well known substance now universally 

 designated as "tuberculin" is the metabolic product (toxin) 

 of the bacillus tuberculosis, elaborated in artificial media. 

 It was first prepared by Koch in 1890, and is now manu- 

 factured by various well known firms, each of which prob- 

 ably uses a special process of preparation. The principles 

 are, however, the same. A pure culture of the bacillus is al- 

 lowed to grow for a certain time, until the media is saturated 

 with the poison (toxin). The living bacteria are killed with 

 heat and then filtered out by passing the mixture through 

 porcelain. It is then evaporated to a certain strength and 

 preserved in sterilized vials with carbolic acid. Tuberculin 

 is an albuminous derivative that is not soluble in alcohol. 

 It seems to be a bacterio-proteid, that differs from the toxal- 

 bumins by resisting excessive heat. Tuberculin is not de- 

 stroyed by boiling for hours. When injected into healthy 

 animals it is C[uite harmless but it proves very poisonous to 

 tuberculosis patients. 



Immunity. — Numerous investigators have experimented 

 with antitubercle serums, hoping to apply the principles of 

 serum therapy to tubeixulosis, but nothing yet achieved has 

 been recognized by either the medical or veterinary profes- 



