PHYSIOLOGY. 21 



certain state of thought. In 696. of the same Institutions, 

 where he defines a disease in general : * Status corporis viventis 

 tollens facultatem exercendae actionis cujuscunque vocatur 

 morbus ;' he adds, in view of some opinions that were then 

 prevailing ' Nee mentio animae facta in hac definitione, quia 

 corporis statum determinatum idem animae status individue co- 

 mitatur.' The other authority, which you can more convenient- 

 ly consult, is Dr. Haller : in 570. of his Primae Lineae Physi- 

 ologiae, after having proved the existence of a soul in the body, 

 he adds these words 4 Et tamen haec anima, adeo diversa a 

 corpore, arctissimis cum eo ipso conditionibus religatur ; quoe et 

 cogitari cogatur ad eas species, quas corpus ipsi repraesentet ; et 

 absque cerebri corporeis speciebus non videatur aut meminisse 

 posse, aut judicare ; et cujus denique voluntas in corpore vel 

 causa, vel occasio velocissimorum maximorumque motuum est.' 

 Now these passages, from Whytt, Boerhaave, and Haller, shew 

 what is the most common system among physicians, that though 

 they think the soul and body to be two distinct substances, yet, 

 during their connexion in a living state, they act upon one an- 

 other by a physical necessity. Dr. Boerhaave explains it, and also 

 Dr. Haller: ' Anima cogitari cogatur ad eas species quas corpus 

 ipsi repraesentet ;' and that the state of the mind produces some 

 corresponding state of the body. Very different is an opinion 

 which has prevailed for the greater part of a century, the author 

 of which may be considered to be Dr. Stahl. He and his followers 

 not only maintain that the motions have their source in the 

 power of the soul so far Dr. Whytt agrees but they go far- 

 ther, in asserting that the soul is not necessarily determined by 

 the state and condition of the body itself, but that the soul 

 merely as present, and as perceiving what is going on, and 

 what motions are conducive to life and health, excites one 

 kind of motion, and puts a stop to another. The principal 

 difficulty that occurs to them is, that the effects of the soul's 

 motions, as Dr. Whytt alleges, are sometimes pernicious to 

 the system. But in these cases they only suppose that the 

 soul is not perfectly regular, that it is not perfectly wise, 

 and so may mistake its purpose or omit the effecting a cure, 

 and that thus many phenomena of the body may occur, 

 independently of any mechanical condition of the body itself, 



