TUBERCULOSIS OF THE EYE 347 



bacilli cannot be demonstrated. The clinical signs give more informa- 

 tion than the bacteriological examination. The inoculation of sus- 

 picious material on a rabbit or guinea-pig is much more valuable as a 

 differentiating test than is the demonstration of the bacilli. 



1. INOCULATION. 



In making an inoculation with material from a superficial lesion, 

 the ulcerated part is first excised or cauterized with the galvano- 

 cautery, so that the pyogenic bacteria may not ruin the test. If we 

 have to do with compact matter, a portion is introduced into the 

 anterior chamber. It is better not to attempt this operation on the 

 luxated eye of the rabbit, as the rise in the tension may cause diffi- 

 culties. The eye is cocainized, and then, without fixation in fact, 

 often without any assistance whatever a small incision can be made 

 up and out, about 1 millimetre from the corneal margin, the globe 

 being merely steadied through the lids. (A deposit on the iris is more 

 easily obtained from a peripheral incision, and makes the test more 

 delicate.) After the escape of the aqueous, some more cocaine is 

 dropped on the site of the incision. In two to three minutes the iris 

 is so anaesthetic that the material can be introduced with a stylet ; the 

 material must not be left too near the incision, as it may be again 

 extruded. The lens must not be injured. 



If pure tuberculous material be introduced, the initial irritation soon 

 disappears, and when the test is positive the well-known nodules 

 appear in fourteen days at the earliest, and sometimes only after 

 three or four weeks ; the nodules are followed, as a rule, by general 

 tuberculosis. 



If the material be very friable, it is better to mix it with physio- 

 logical salt solution and inject obliquely into the anterior chamber 

 after the aqueous has been allowed to flow away through the cannula. 

 The fluid can be injected into the peritoneal cavity of a guinea-pig ; 

 many consider that this latter method gives a more delicate test. 

 It certainly has the advantage that much more material can be intro- 

 duced, though the former method has the advantage that the resulting 

 process can be much more easily observed. 



Gourfein, Morax, and Chaillous recommend, in the diagnosis of the 

 tubercular nature of an iritis, that the aqueous be drawn off with a 

 syringe and injected into the anterior chamber a rabbit. They report 

 positive results. We have definitely shown that this may fail in cases 

 whichare certainly tubercular. 



Although the positive evidence is so strong, a negative result is no 



