532 Tuberculosis. 



The term tuberculum was formerly applied to every possible and conceivable 

 form of nodule or tumor. In 1794 Baillie and in 1810 Bayle applied this term 

 exclusively to the small gray nodule which occurs in tuberculosis. Later on Laiinneo 

 regarded the cheesy substance as characteristic of tuberculosis and finally Virchow 

 laid particular stress upon the fact that the tubercle was composed of small cells 

 resembling lymph cells and that the structure was de^^ipid of a vascular supply. 

 He regarded the tubercle as characteristic of tuberculosis. Langhals called attention 

 to the frequent occurrence of giant cells in the tubercle. Schueppel laid especial 

 stress on the importance of the frequently observed epithelioid cells. According 

 to the latter a true tubercle ■ consisted of one or several giant cells surrounded by 

 one or more rows of large epithelioid cells which latter were again bound by a 

 zone of small round cells. As a matter of fact, however, giant and epithelioid 

 cells may be absent from true tubercles, and giant cells occur also in other patho- 

 logical formations. Ziegler showed that the tubercle was the result of an inflam- 

 matory process, originating like ordinary inflammatory granulation tissue, that is, 

 principally from migrated white blood corpuscles and that other tissue elements such 

 as the endothelial cells of the lymph vessels played only a subordinate role in the 

 construction of the tubercle. According to him the true tubercle was characterized 

 by its non-vascularity and by its tendency to undergo cheesy degeneration. Baum- 

 garteu maintains that the tubercle bacillus gives rise to a proliferation of the fixed 

 connective tissue cells exclusively (epithelial as well as connective tissue proper) 

 which produce the so called epithelioid and giant cells and that the peripheral zone 

 of round cells consists of white blood corpuscles which emigrated subsequently. 

 Finally, according to Metschnikoff, the epithelioid and giant cells are phagocytes 

 of mesodermal origin which are attracted by the positive chemotactie action of 

 the tubercle bacilli which they take up into their substance. 



Nodules resembling tubercles will also develop around dead bacteria and 

 around inorganic foreign bodies. These nodules however do not undergo cheesy 

 degeneration, have no progressive tendencies and cannot be transmitted by inocu- 

 lation ! 



In recent times it has been pointed out by various investigators, 

 especially Weiehselbaum and his pupils, that tubercle bacilli may exist 

 for a long time in a dormant state -in the lymph glands without causing ^ 

 the development even of microscopical tubercles. Before the discovery 

 of the tubercle bacillus Orth demonstrated by inoculation experiments 

 that lymph glands of normal appearance may contain microscopic tu- 

 bercles (1876) ! The effects of the tubercle bacilli can manifest them- 

 selves only in lymphoid hyperplastic processes ("lymphoid stage of 

 tuberculosis" — Bartel & Spieler). This stage may have a variable dura- 

 tion, may even retrogress and possibly exert an immTinizing effect. The 

 process may, however, with or without subsequent infection lead to the 

 development of specific tuberculous changes at that point or in remote 

 parts of the body. Microscopically, glands in the lymphoid stage of in- 

 fection appear either entirely normal or show only a homogeneous 

 swelling. Tubercle bacilli can be demonstrated by inoculation only. 

 Joest doubts the occurrence of such a lymphoid stage at least in animals 

 with generalized tuberculosis, especially in cattle and swine. He exam- 

 ined 27 such glands in cattle and 4 in pigs and found specific histolog- 

 ical tuberculous changes in all of them (epithelioid tubercles with giant 

 cells). Jonske found the same condition in five glands that produced 

 inoculation tuberculosis. Smit failed to find histological tuberculous 

 changes in seven swollen and hyperemic glands, and Rievel and Linnen- 

 brink could not discover microscopical tuberculous lesions in three out 

 of twelve such glands that had a normal appearance. 



That lymph glands may be virulent without exhibiting microscopic 

 tubercles has been proven by investigations of Frothingham, Calmette, 

 Guerin & Delearde. These experiments were made in calves, but the 

 inoculations with human tubercle bacilli proved that they may remain 

 latent in the body for months and, according to Lignieres, even for a 

 year. Virulent bacilli may be found in partially calcified lesions (Baum- 



