248 Human Frame* 



all this is done by that insect with ati 

 equal consciousness of the manner how, 

 as the similar voluntary actions of man 

 are effected. 



Nor are the involuntary motions less 

 mysterious and wonderful. The sto- 

 mach, the intestines, and all the functions 

 necessary to life, wait not to be called in- 

 to action by any volition of ours. The 

 heart, placed near the centre of the sys- 

 tem, performs its task as well ..when we 

 are asleep, as when we are awake, by night 

 as by day, and like an unwearied and 

 iaithful labourer, with muscular exertions 

 distributes the vital stream through our 

 complicated frame, 'till their wearied 

 functions cease, and the tenement of clay 

 is inhabited no more. How admirably 

 It is calculated to keep up this continued 

 circulation throughout the system may 

 be understood by the following computa- 

 tion by Dr. Keill: u Each ventricle will 

 at least contain one ounce of blood. The 

 hearts contracts four thousand times in 

 one hour ; from which it follows, that 

 there passes through the heart, every 

 hour, four thousand ounces, or three 

 hundred and fifty pounds of blood, Now 



