582 Tuberculosis. 



until it I'egins to drop again, the object of ouv observations being to determine 

 the highest temperature reached after the injection of the tubercuHn which is 

 possible only by following this rule. Tn order to obtain accurate results for 

 comparison of temperature, the same thermometer should always be used for the 

 same animal throughout a test. Animals should not be watered immediately before 

 taking the temperature. 



In sucking calves the results of tests are less reliable for which reason it 

 is best to defer the test until they are si.x months of age. Animals with clinical 

 symptoms of tuberculosis, very old and very emaciated animals may give very 

 unreliable or unexpected results and for practical purposes might as well be excluded 

 from the test. 



Malm and Kitt recommend the intravenous injection of tuberculin on account 

 of the earlier appearance of the reaction. If for example the tuberculin is injected 

 from 7:00 to 9:00 A. M. the reaction may set in between 12:00 noon and 5:00 P. M. 



(The dose of American commercial tuberculins is usually indicated in the 

 instructions furnished by the manufacturers.) 



2. The Ophthalmic Tuberculin Test (Oplithalmoreaetion. 

 Conjunctival Reaction). Wolff-Eisner (1907) and almost sinnil- 

 taneonsly Calmette also observed that a few drops of tuberculin 

 applied to the conjunctival sac of tuberculous persons produced 

 an inflammatory reaction manifesting itself in reddening and 

 swelling of the conjunctiva. During the same year Vallee 

 demonstrated that a similar reaction takes place in cattle and 

 subsequent investigations of other authors have shown that 

 this test is quite valuable for diagnostic purposes, especially 

 when concentrated bovine tuberculin is used. A pronounced 

 positive reaction to this test may be considered as almost con- 

 clusive evidence of the presence of tuberculosis. However, 

 since animals known to be affected with tuberculosis may not 

 very infrequently give negative reactions to this test, the alv 

 sence of a positive reaction does not necessarily exclude tuber- 

 culosis. 



In cattle the conjunctival reaction usually sets in between the 

 6th and 9th hour or a little later. It manifests itself in watering of 

 the eyes, reddening and edematous swelling. Later, lietween the 12tli 

 and 24th hour there is a production of purulent secretion which accumu- 

 lates under the nasal canthus of the eye in the form of an elongated 

 mass (see Plate III) which finally drops off or dries up to form a 

 yellow crust. The reaction continues until the 36th to 48th hour or 

 even three or four days. To be positive the reaction must consist of 

 a purulent conjunctivitis (polynuclear leucocvtes in turbid yellow 

 exudate). A catarrhal inflammation attended only with profuse water- 

 ing of the eyes or mucous exudate, especially if concentrated tuberculin 

 has been used, may follow in perfectly healthy animals. The severity 

 of the conjunctivitis is of course no indication of the extent, or stage, 

 of the tuberculous process. A simultaneous, or a previous subcutaneous 

 injection of tuberculin has no effect on the conjunctival reaction, except 

 that in some instances the conjunctivitis is even more pronounced. 

 Occasionally when the subcutaneous test is applied to tuberculous ani- 

 mals that have previously reacted to the conjunctival test the ophthalmic 

 symptoms may again manifest themselves. As a result of hypersensi- 

 tiveness of the conjunctiva following the eye test a repetition of the 

 latter may result in a more pronounced reaction than before. The 

 conjunctival reaction, even if excessive or severe, does not affect the 

 general condition of the animal nor reduce the secretion of milk. 



