320 HISTOLOGY OF THE MORBID PROCESSES. 



may also cause serohsemorrhagic exudations from the serous 

 membranes e. g., the pleura; but the most characteristic tissue- 

 reaction due to its presence is the formation of the tubercle. This 

 is the result of a rejuvenescence of the connective-tissue cells, 

 without any preceding exudation, and an attempt at the pro- 

 duction of granulation-tissue around the bacilli (Figs. 282 and 

 283). These multiply so slowly that they and their products exert 

 merely an irritation on the cells of the tissue, stimulating them 

 to reproduce, but they do not usually cause the growth of new 

 bloodvessels, so that in the majority of cases the granulation-tis- 

 sue is not vascularized. Furthermore, as they increase in number 

 the bacteria cause degenerative and necrotic changes in the cells 

 that have been produced, and, as their products increase in 

 amount, the cells in the centre of the focus of inflammation are 

 destroyed (cheesy degeneration, p. 274), while those at the periph- 

 ery multiply, causing an increase in the size of the inflamma- 

 tory nodule or tubercle. The multiplication of the cells is often 

 hindered to a certain extent by the poisons present; the nuclei 

 divide, but the protoplasm fails to undergo a corresponding di- 

 vision. In this way multinucleated cells, called " giant-cells/ 7 are 

 produced. 



As the result of these processes a developing tubercle presents the 

 following appearances under the microscope. In the centre is a 

 mass of cheesy matter, composed of fine granules of fat, albuminoid 

 material, and fragments of nuclei, the result of degenerative and 

 necrotic changes caused by the bacterial poisons. Around this 

 mass is a zone of rather large " epithelioid " cells, which belong to 

 the granulation-tissue, and among which there may be a variable 

 number of emigrated leucocytes, probably attracted by the necrosed 

 tissues in the centre. Also, near the centre or in the granulation- 

 tissue, a few giant-cells may be present ; but they are not invariably 

 found, nor is their presence a conclusive sign that the process is 

 tubercular (Fig. 284). 



The ultimate outcome of the process varies in different cases. 

 The inflammatory reaction may overcome the infection, encapsulat- 

 ing the nodule with a dense cicatricial tissue ; or the infection may 

 conquer ; bits of the cheesy matter containing tubercle bacilli may 

 then find entrance into the lymphatic circulation and be carried to 

 the neighboring lymph-glands, establishing in them new foci of 

 tubercular inflammation, or tubercle bacilli may get into the blood- 



