DISEASES OF THE BLOOD. 127 



tive, being either calcareous, caseous, or softening. These 

 changes have nothing specific about them, with the excep- 

 tion, perhaps, of the softening, the product of which is a 

 special kind of purulent fluid. The frequency of casea- 

 tion and calcification account for the chronic tendency of 

 scrofula. We must now determine what the tubercle is. 

 Some says it results from changes of epithelial cells, 

 others from connective-tissue corpuscles, others consider 

 it a special materies morbi deposited from the blood or 

 formed anew in a formative extravasated fluid, and some 

 say it is a hyperplasia of lymphoid tissue. Gerlach says, 

 " the presence of a tubercle virus is evident.^'' There are 

 other theories of its nature. In the state of the question 

 we may be allowed to take the view which most readily 

 chimes in with clinical facts, and consider tubercle cells 

 specific organisms resembling those of cancer, to which 

 the large cells sometimes seen in tuberculous matter are 

 remarkably similar. The pathological analogies between 

 cancer and tubercle are very marked; Jones says ^' a 

 tubercle thus seems to be a structure intermediate between 

 the products of inflammation, and the new growths pro- 

 perly so-called being less transitory than the former, less 

 permanent than the latter, and less capable of develop- 

 men than the latter.-*^ Sanderson indicates three essentials 

 to the development of tubercle — a constitutional predis- 

 position, local irritation, and subsequent infection. A 

 freshly developed tubercle consists of animal matter, 

 albumen, fibrin and fat, and earthy matter, insoluble 

 phosphates and carbonates of lime, and the soluble salts of 

 soda (Glover). Calcification consists in increase of the 

 earthy and decrease of the animal matter. " Grey 

 tubercle '^ results from caseation ; the fat has considerably 

 increased. The fact that infiammatory products undergo 

 these retrograde metamorphoses has long complicated the 

 pathology of scrofula; many pathologists still hold that 

 tubercle owes its origin to the absorption of metamor- 

 phosed products of inflammation. Diagnosis of scrofula 

 post-mortem must be based on the presence of the 

 miliary tubercle. Hence, a doubt frequently exists as to 



