252 PRACTICE OF PHYSIC. 



" The red vessels of the lungs are very liable to rupture in 

 any case of increased impetus ; but the pouring out of blood, 

 either by anastomosis or by rupture, may readily happen when- 

 ever the extremities of the blood-vessels of the lungs are any- 

 how pressed or straitened. And they may be so to a consider- 

 able degree by a neighbouring tubercle ; and thus, without a 

 preceding determination, or any phlogistic state, the haemoptysis 

 may occur. I have thus given you an idea how a spitting of 

 blood may be founded on a tubercle ; and every body knows it 

 to be the nature of the scrofulous tumour, that it readily changes 

 into an ill-conditioned ulcer. But to explain all that relates to 

 phthisis, I add, that scrofulous tubercles are not the only ones 

 necessary. Indeed, I must own, that in many cases, it can 

 hardly be supposed that the number of tubercles which we find 

 in the whole cellular texture of the lungs can all be tumified 

 glands. We are led to suppose another cause of tubercles : 

 Here is one which I think sufficiently obvious. We observe, 

 that frequently, in consequence of a particular state of balance 

 of the system, a determination is made to the lungs, which pours 

 out red blood by anastomosis or rupture. Now we can conceive, 

 that this determination, in a lesser degree, may be sufficient to 

 produce some effusion into the cellular texture, not sufficient to 

 be forced into the bronchiae. Now, whenever such effusion hap- 

 pens in consequence of such weaker determination of a fluid 

 (as we can easily conceive), which is not fit to be again re- 

 absorbed, it will accumulate till it has formed for itself a little 

 cyst, or what would otherwise be called a tubercle, which, like 

 the scrofulous tubercle, will straiten and compress the neighbour- 

 ing blood-vessels, and at length produce the actual haemorr- 

 hagy. I own that this is in some measure hypothetical. An- 

 other cause, more certain in fact, is a matter of frequent observa- 

 tion, viz. this that tradesmen exposed to much dust are peculiar- 

 ly liable to phthisis, without any other predisposition in consti- 

 tution or other occurrences in life. I think that in these cases 

 the phthisis may be imputed to the dust getting into the lungs, 

 adhering to and stopping up some corner of the bronchias, and 

 there laying the foundation to tubercles, by forming such cysts, 

 or by irritating the neighbouring vessels, and so causing the 

 congestions which give the appearance of tubercle. 



