210 PRACTICE OF PHYSIC. 



artery, or between the vessels of the lungs and those of all the 

 rest of the body. And although the lesser capacity of the ves- 

 sels of the lungs is commonly compensated by the greater ve- 

 locity of the blood in them ; yet, if this velocity be not always 

 adjusted to the necessary compensation, it is probable that a 

 plethoric state of the whole body will always be especially felt in 

 the lungs ; and, therefore, that an hasmorrhagy, as the effect of 

 a general plethora, may be frequently occasioned in the lungs, 

 even though there be no fault in their conformation. 



DCCLXI. In some cases, perhaps, an haemorrhagy from the 

 lungs, or an haemoptysis, does arise from the general plethoric 

 state of the body ; but an haemoptysis more frequently does, 

 and may be expected to happen, from a faulty proportion be- 

 tween the capacity of the lungs and that of the rest of the body. 



DCCLXII. When such a disproportion takes place, it will 

 be evident, that an haemoptysis will especially happen about the 

 time that the body is approaching to its acme ; that is, when 

 the system of the aorta has arrived at its utmost extension and 

 resistance, and when, therefore, the plethoric state of the whole 

 must especially affect the lungs. 



DCCLXIII. Accordingly, it has been constantly observed, 

 that the haemoptysis especially occurs about the time of the 

 body's arriving at its acme ; but I must remark also, that the 

 haemorrhagy may occur sooner or later, according as the balance 

 between the vessels of the lungs, and those of the system of the 

 aorta/, happen to be more or less exactly adjusted to one another ; 

 and it may therefore often occur much later than the period 

 mentioned, when that balance, though not quite even, is how- 

 ever not so ill adjusted, but that same other concurring causes 

 are necessary to give it effect. 



DCCLXIV. It was anciently remarked by Hippocrates, 

 and has been confirmed by modern observation, that the 

 haemoptysis generally occurs in persons between the age of 

 fifteen and that of five-and-thirty ; that it may happen at any 

 time between these two periods ; but that it seldom happens 

 before the former, or after the latter ; and it may be proper 

 here to inquire into the reason of these two limitations. 



DCCLX V. With respect to the first, the reason of it has 

 been already explained in DCCLXII. and DCCLXIII. 



