426 PRACTICE OF PHYSIC. 



but sometimes arising from, and particularly modified by occur- 

 rences in the course of life. 



MCCCXI. This mobility consists in a greater degree of 

 either sensibility or irritability. These conditions, indeed, phy- 

 sicians consider as so necessarily connected, that the constitu- 

 tion, with respect to them, may be considered as one and the 

 same. But I am of opinion that they are different ; and that 

 mobility may sometimes depend upon an increase of the one, 

 and sometimes on that of the other. If an action excited, is, 

 by repetition, rendered more easily excited, and more vigorous- 

 ly performed, I consider this as an increase of irritability only. 

 I go no farther on this subject here, as it was only necessary to 

 take notice of the case just now mentioned, for the purpose of 

 explaining why epilepsy, and convulsions of all kinds, by being 

 repeated, are more easily excited, readily become habitual, and 

 are therefore of more difficult cure. 



MCCCXII. However we may apply the distinction of sen- 

 sibility and irritability, it appears that the mobility, which is the 

 predisponent cause of epilepsy, depends more particularly upon 

 debility, or upon a plethoric state of the body. 



MCCCXI 1 1. What share debility, perhaps by inducing sen- 

 sibility, has in this matter, appears clearly from hence, that 

 children, women, and other persons of manifest debility, are the 

 most frequent subjects of this disease. 



MCCCXI V. The effect of a plethoric state in disposing to 

 this disease appears from hence, that plethoric persons are fre- 

 quently the subjects of it ; that it is commonly excited, as I 

 have said above, by the cause of any unusual turgescence of 

 the blood ; and that it has been frequently cured by diminish- 

 ing the plethoric state of the body. 



That a plethoric state of the body should dispose to this dis- 

 ease, we may undertand from several considerations. 



ls, Because a plethoric state implies, for the most part, a 

 laxity of the solids, and therefore some debility in the moving 

 fibres. 



2dly, Because, in a plethoric state, the tone of the moving 

 fibres depends more upon their tension than upon their inher- 

 ent power : and, as their tension depends upon the quantity 

 and impetus of the fluids in the blood-vessels, which are very 



