Comparative Value of Tests. 587 



cutaneous test. It cannot be denied, of course, that the applica- 

 tion of this method is attended with certain objections or at 

 least inconveniences, viz., the long time required to make the 

 observations, the repeated recordings of temperature required, 

 and finally thefact that positive reactions reduce, temporarily, 

 the yield of milk from the animals in question. 



Since none of these disadvantages are presented by the 

 various local tests, it is advisable, in practice, where large 

 herds are to be tested, to apply a local test first, preferably 

 the intradermal (intracutaneous) or the ophthalmic test. Thus. 

 after the great majority of tuberculous animals have been recog- 

 nized the remainder of the herd may be subjected to the sub- 

 cutaneous test and the examination of the herd be completed. 

 Such a procedure is the more admissible since the occurrence 

 of a thermic reaction is in no way prevented or interfered with 

 by the previous local test. 



(The above arguments would hardly apply, with equal force, to c.onditions as 

 they exist in America at the present time. — Translator.) 



Agglutination Test. According to the investigations of Arloing & Courmont 

 the blood serum or pleural exudate of tuberculous persons or animals when added 

 to homogeneous liquid cultures causes clumping of the tubercle bacilli and their 

 precipitation to the bottom of the vessel, leaving the previously turbid fluid clear 

 and transparent (agglutination) while the blood serum of healthy individuals does 

 not possess this property. On the basis of these observations these authors recom- 

 mended the agglutination test as a practical means of diagnosing latent tuberculosis, 

 ^n one of their series of experiments the blood serum of thirty healthy calves did 

 pot, in any case, agglutinate a culture when added in proportions of one to five 

 while the serum from 70 mature cows, with only one exception, agglutinated cultures 

 when added in volumetric proportions of one to ten or even thirty. 



Other authors (Beck & Eabinowitsch, Panisset) could not confirm the diagnostic 

 value of this method nor has the same been found of any practical importance in 

 human medicine. 



Precipitation Reaction. According to Bonome the blood serum of tuberculous 

 persons or animals produces a more or less conspicuous clouding and precipitation 

 when added to a filtered emulsion made of fresh cheesy tubercles or cultures of" dried 

 tubercle bacilli mixed with 5% glycerin. The serum of healthy individuals either 

 does not possess this property at aU or only to a slight degree. It is claimed 

 for this test, also, that when .pure cultures of tubercle bacilli are used it is possible 

 to differentiate between infection with human tubercle bacilli and infection with the 

 l)0vine type. 



Calmette & Massol, Valine and also Jousset found that the serum of highly 

 immune animals contained a thermolabile substance which produces decided precipita- 

 tions in solutions of tuberculin as well as in non-concentrated tuberculosis bouillon 

 and in bacillus extracts. In the bodies of tuberculous animals, however, it seems 

 to be present in such small and variable quantities that precipitation experiments 

 give too irregular results to be of value for diagnostic purposes. In correspondence 

 with this statement the results obtained by Zwick in his experiments with the serum 

 of a cow with advanced tuberculosis were negative throughout. 



Complement Fixation and Opsonins. Valine was able to demonstrate anti- 

 bodies in the serum of highly immunized horses (Hennepe the same in the serum 

 of calves treated with bovo-vaccine) which had the power to fix guinea pig comple- 

 ments with strains of the tubercle bacilli that had been used in the immunizing 

 process as antigen. Bach, however, found that sera from cattle free from tuberculosis, 

 as well as that from shghtly or extensively affected cattle manifested the same 

 peculiarities in complement fixation experiments, and that this action was not specific. 

 At present, therefore, this method has no more diagnostic value than the opsonic 

 index of the blood of tuberculous animals, the study or investigation of which latter 

 has as yet received very little attention in veterinary medicine 



Sfrubell & Felber have coadueted a series of investigations alonp this line with 

 80 beef cattle, without however getting clear or decisive results. Of the tuberculous 

 cattle 83.3% showed tuberculo-opsonic indexes to human tubercle bacilli ranging 



