STATE HYGIENE 579 



serious as the former, as an advanced case may be 

 diagnosed clinically. 



A tuberculous animal injected with tuberculin gets as a 

 result a febrile reaction. It is the character of this febrile 

 reaction on which the diagnosis is based, and it is in 

 judging of the febrile reaction that error in non-expert 

 hands may occur. 



The first essential is to know the animal's temperature 

 before injection, and its usual daily variations. When this 

 has been ascertained the tuberculin temperature offers 

 little difficulty, provided that we pay less attention to the 

 height the mercury rises, and every attention to the manner 

 in which it rises. The rise should be gradual, the tempera- 

 ture being taken at the 6th, 9th, 12th, and 15th hours, the 

 maximum point being reached at the 12th or 15th hour 

 after inoculation, after which it gradually falls to normal. 

 Where the thermometric curve is an irregular rise and fall 

 such a temperature is not tubercular. 



It is of supreme importance that the animals should be 

 free from fever, not exposed to sudden variations of tempera- 

 ture, and living under their ordinary conditions ; very little 

 change in their mode of life will cause the temperature to rise, 

 and no more potent cause of this can exist than strange or 

 unusual surroundings. Fig. 189 shows a temperature curve 

 of a tuberculous animal after the use of tuberculin, and 

 also that of an animal injected with tuberculin but non- 

 tuberculous. 



McFadyean found that an animal infected with a large 

 dose of bacilli reacted to tuberculin eight days afterwards, 

 but it by no means follows that a case will react in this 

 short time to infection naturally contracted. 



Even after the exercise of due care there may be certain 

 doubtful cases which will require retesting, but this should 

 not be applied for a month or more after the first inocula- 

 tion, as the animal may acquire a high degree of tolerance 

 to tuberculin. The indications for retesting are where the 

 temperature curve is suspicious, but not typical, and where 

 a temperature of less than 104° F. is obtained. 



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