8 PHYSIOLOGY, 



it is the brain and the nerves, thus connected, that we call the 

 nervous system, I think it is with some propriety that I have 

 allotted my second section to treat" 



2. Of the nervous system, in which the motions of the body 

 for the most part begin, and upon which the motions produced 

 in it chiefly depend. " We consider this as it is acted upon by 

 other bodies, or as it acts upon these." 



3. Of the motion and circulation of the blood ; and of the sev- 

 eral organs and actions employed in supporting it. " For a 

 long time past since the discovery of the circulation of the 

 blood most physicians have viewed this as the function upon 

 which all the rest depend; and perhaps there is not one entirely 

 independent of it. But the action of the heart depends upon 

 the nerves, and these upon the brain, so that the heart depends 

 upon the energy and action of the brain. The brain, on the 

 other hand, would not long be capable of its functions, if it were 

 not for the circulation of the blood. The consideration of the 

 circulation of the blood, which must be taken abstractedly from 

 the nature of the fluids, naturally leads to the consideration of 

 these; and whilst a considerable quantity is necessary to be 

 present, th^re is a daily and considerable waste. For we find 

 by experiments that the body loses of its weight, and especially 

 by a waste of the fluid parts. We also perceive another de- 

 mand for a quantity of fluids. The body, from a small begin- 

 ning, rises to a considerable bulk, and all this in a certain 

 course of life, which must be effected by the addition of a quan- 

 tity of matter to it ; and we can find no other source for sup- 

 plying this growth, but the matters taken into the mouth, which 

 common observation presumes to be destined for this purpose, 

 and calls aliments. But they are not of the nature of the body, 

 and must be converted into the same nature by the body itself. 

 So that in considering the body, as supplied and supported by 

 the aliments, we must consider the functions necessary to con- 

 vert the aliments into the nature of the animal fluids : there- 

 fore, we come next to treat" 



4. Of the functions employed in supporting and repairing the 

 several solid and fluid matters of the body ; and, on this occasion, 

 of the nature of the several fluids themselves. 



