214 PRACTICE OF PHYSIC. 



heads and short necks, and to men in the decline of life, when 

 the powers promoting the motion of the blood are much weaken- 

 ed. 



DCCLXXIII. I have thus attempted to give the history of 

 the plethoric and haemorrhagic states of the human body, as 

 they occur at the different periods of life ; and hope I have 

 thereby explained not only the nature of haemorrhagy in general, 

 but also of the particular hoemorrhagies which most commonly 

 appear, and as they occur successively at the different periods 

 of life. 



SECT. III. OF THE REMOTE CAUSES OF H.EMORRHAGY. 



DCCLXXIV. In the explanation hitherto given, I have 

 especially considered the predisposition to haemorrhagy ; but it 

 is proper also, and even necessary, to take notice of the occa- 

 sional causes, which not only occur with the predisponent, in 

 exciting haemorrhagy, but may also sometimes be the sole causes 

 of it 



DCCLXXV. These occasional causes are, 



1. External heat, which, by rarefying the blood, produces or 

 increases the plethoric state of the body ; and the same heat, as 

 giving a stimulus to the whole system, must urge any particular 

 determinations before established still further, or may urge to 

 excess any inequality otherwise innocent ; so that in either way 

 external heat may immediately excite haemorrhagies, to which 

 there was a predisposition, or may form congestions where there 

 were none before, and thereby occasion haemorrhagy. 



2. A considerable and sudden diminution of the weight of the 

 atmosphere, which seems to occasion the same effects as heat, by 

 producing also an expansion of the blood. 



3. Whatever increases the force of the circulation, and there- 

 by the velocity of the blood, may operate in the same manner 

 as heat, in urging not only previous determinations with violence, 

 but also in urging to excess inequalities otherwise innocent. 

 All violent exercise, therefore, and especially all violent efforts, 

 which, not only by a larger and longer inspiration, but also by 

 the simultaneous action of many muscles interrupting the free 

 motion of the blood, impel k with unusual force into the ex- 



