322 HISTOLOGY OF THE MORBID PROCESSES. 



escapes into the alveoli or bronchi cavities are produced. The proc- 

 ess rarely remains a purely tubercular one in the lungs. The con- 

 ditions there (exposure to inspired air) are favorable to a mixed 

 infection with pyogenic bacteria, which hastens the destruction of 

 the pulmonary tissues inaugurated by the tubercle bacillus. 



Isolated tubercles, such as have been described, are not infre- 

 quently met with ; but it is more usual to find a number of such 

 nodules in close aggregation, each starting from a distinct focus of 

 infection. As these enlarge, their peripheries coalesce, and finally 

 their cheesy centres meet and blend. Meanwhile fresh young 

 nodules are formed around the older mass, and thus the tubercular 

 disintegration of the tissues spreads. It is for this reason that 

 tubercular ulcers e. g., of the intestine have swollen and under- 

 mined borders (Fig. 285). 



FIG. 285. 



Tubercular ulcer of the intestine. (Kaufmann.) The cavity of the ulcer was formed 

 through disintegration and removal of the cheesy matter formed in the earlier tuber- 

 cles. Now the base of the ulcer is formed by necrosed and cheesy material, beneath 

 which eight or nine distinct tubercles are distinguishable, those in the centre extending 

 into the muscular coat of the intestine. The infection has also extended into the lymph- 

 atics beneath the serous coat, where three tubercles can be seen. 



The other granulomata have peculiarities due to their special 

 causes, which are pretty clearly defined in typical cases ; but, as 

 in tuberculosis, these inflammations may in certain instances be 

 structurally indistinguishable from those due to other causes. 



Chronic Inflammation. 



A consideration of the infective granulomata makes the fact clear 

 that inflammation may occur without the production of a distinct 

 exudate, the damaging cause merely exciting the tissues to prolifer- 

 ation ; but in that group of inflammations the excitation of the tis- 

 sues was sufficiently intense to occasion the development of a tissue 

 closely resembling the granulations of acute inflammation. For 

 this reason they were designated as subacute inflammations. 



There is another group of inflammations in which the irritation 

 of the tissues is not sufficient to induce a rejuvenescence of the 

 cells in such a pronounced degree as to cause their reversion to a 



