16 ARTIFICIAL PRODUCTION OF TUBERCLE. 



Under the microscope (Plate III. figs. 1, 2, 3), the granulations are found 

 scattered in the course of the vessels, and they then originate in the perivas- 

 cular sheath. They are also, however, to be found in parts of the tissue 

 where no vessels whatever are to be seen, and here they appear to have their 

 starting point from masses of nuclei or cells agglomerated among the meshes 

 of the omentum, wliich appear normally to occur in scattered points of this 

 tissue. Erom both sources, the growth extends irregularly to the surrounding 

 tissue ; and whatever their origin, whether from the sheaths of the vessels, or 

 independently of these, the only further change discoverable consists in a 

 dense agglomeration, most commonly of the nuclei, and sometimes of the 

 cells, in the meshes of the network of which the omentum is composed. 

 With this exception, I have never been able to trace any distinctive characters 

 which separate the histological characters of tubercle in the omentum from 

 that of the healthy surrounding tissues. I have never seen anything like an 

 epithelium covering the omentum, as distinct from any nucleated tissue 

 beneath. The only appearance which we can see in the normal omentum is 

 that of cells (the outline of which is often indistinct, and of which the nuclei 

 alone may be visible) imbedded in the meshes of a fibrillated tissue — a 

 structure which strongly resembles that which ordinarily is called " lymphatic 

 tissue." The cells, both in the normal and also in the tubercular omentum, 

 vary somewhat in size ; but their average is between l-24!00th and l-3200th 

 of an inch in diameter. 



To present you briefly with a summary of the number of times in which 

 these appearances have been found. Out of the 117 cases, three internal 

 organs have been affected fifty-eight times ; in six, less than three. Out of 

 these sixty-four cases, local granulations at the site of injury have been stated 

 to be present forty-one times. They were absent in all the doubtful cases. 

 They were absent in the case of general tubercle following the insertion of 

 a cotton-thread, though the fibrous tissue in which this was imbedded 

 presented some indistinct traces of their appearance. They were absent, 

 also, in three out of four cases, where tubercle followed the insertion of 

 a cotton-thread saturated with vaccine-lymph. They were never present 

 when no certain internal eflfect was produced, except in one doubtful case in 

 a rabbit. 



The local lymphatic glands are noted to have been aflfected with induration 

 and cheesy spots in fifty -four cases. In one or two of the doubtful cases, 

 there was induration ; in two others, enlargement, but no other change. In 

 three others of the doubtful cases, they Avcre distinctly aflfected. They are 

 only stated to have been absent in four cases of general tuberculosis ; and I 



