only an increase of insensible perspiration I Have 

 we discovered, why one part of mankind have black 

 skins, and the other white? It is not owing to the 

 climate : for both black men and white are .born in 

 the same latitude. And have not negroes the same 

 flesh and blood with us] But what isjlesh f That 

 of the muscles in particular? Are the fibres, out of 

 which it is woven, of a determinate size ? So that, 

 when you have divided them into smaller and smaller, 

 to a certain point, you come to those of the smallest 

 kind ? Or are they resolvible (at least in their own 

 nature) into smaller and smaller in infinitum ? How 

 does a muscle act ? If you say, by being inflated, 

 and consequently shortened : I ask again, But what 

 is it inflated with ? If with blood, how and whence 

 comes that blood ? And what becomes of that 

 blood, whither does it go, the moment the muscle is 

 relaxed ? What is Hood ? Of how many sorts of 

 particles does it essentially consist ? Of red globules 

 and serum? But in the famous instance, the man* 

 bled at the nose, till what was discharged had no 

 redness left. By what force is the circulation of the 

 blood performed ? Can any one suppose the force 

 of the heart, is sufficient to overcome the resistance 

 of all the arteries? Are the nerves pervious, or 

 solid ? How do they act ? By vibration, or trans- 

 mission of the animal spirits? What are the animal 

 spirits ? If they have any being, are they of the 

 nature of blood, or ether ? What is sleep ? Wherein 

 does it consist I W r e do not enquire, What are tb$ 



