692 EXPERIMENT STATION RECORD. 



form, and in the greater resistance of this form to modifying influences of culture- 

 media; biologically, in a greater resistance to artificial cultivation and in a much 

 greater pathogenic activity toward rabbits, guiuea pigs, and cattle. 



"There is proof, furthermore, of the existence of slightly varying characters even 

 within the varieties proposed. Among the bovine forms studied slight variations 

 in virulence were noticeable. Among the sputum forms, variations in size, in capac- 

 ity for cultivation, and in pathogenic activity have been observed. ... In spite 

 of these variations, mammalian tubercle bacilli may still be considered as forming 

 a fairly compact group when compared with the tubercle bacilli of birds, which are 

 but slightly virulent toward the guinea pig, so susceptible to the mammalian 

 type. . . . The bovine type differs from the human bacilli in a far less saprophytic 

 growth. In the pathological secretion and in the caseous masses the bacilli are 

 relatively scarce. This difference may be a result of their adaptation to the bovine 

 body, in which cavities of the lungs and catarrh of the air tubes are far less com- 

 mon. In other words, certain differences in the type of reaction tend in the one case 

 to make the human bacillus more saprophytic, the bovine more parasitic." 



A study of normal temperatures and the tuberculin test, C. E. 



Marshall (Michigan Sta. Bui. 159, pp. 347-390). — A general discussion 

 of tuberculin and its use is followed by a detailed report of a study of 

 the variations in normal temperature of cattle and a comparison of 

 these results with the variations in temperature after injecting tuber- 

 culin. It was found that normal maximum temperatures varied from a 

 fraction of a degree to over 5°. 



"Owing to this great variation in normal maximal temperatures, we feel justified 

 in bidding caution to all operators in the tuberculin test. The too prevalent method 

 of finding the maximal temperatures of the day of and the day after injection and 

 condemning animals in accordance with this standard, without any further investi- 

 gation, may be the means of unnecessary destruction of property. There are cases 

 where this would be legitimately allowable, as we shall see later in a survey of 

 reactions, but when it is applied irrespective of other features it can not be justified. 

 Where there is a possibility of 5° of variation in normal maximal temperatures, 2° 

 can not be taken as the sole criterion for placing the stamp of 'tuberculous' upon 

 an animal." 



Sudden changes in temperature, the influence of seasons or atmos- 

 pheric temperature upon the temperature of animals, time of day when 

 maximum and minimum temperatures occur, and whether temperatures 

 higher or lower occur on the second day of the test are also discussed 

 with reference to the temperature records kept at the station. 



In summarizing the discussion the following tentative conclusions are 

 advanced : 



"(1) Tuberculin is the best diagnostic known for tuberculosis. 



" (2) Tuberculin itself may be infallible, but its application and interpretation are 

 not. 



" (3) An arbitrary point of condemnation is unwarranted. 



"(4) To succeed iu eradicating tuberculosis from a herd, the tuberculin test must 

 be applied persistently at intervals for as yet an undetermined time. 



"(5) The slaughtering of animals reacting to tuberculin is not justified, unless the 

 physical condition of the animal confirms the tuberculin test and makes it a wise 

 precaution. Reacting animals should be isolated. Should a second test diagnose 

 tuberculosis, slaughter is possibly made justifiable unless the animal is sufficiently 

 valuable to isolate her for offspring or in hopes of recovery." 



