56 THE PHILOSOPHY 



From this outlme, feme idea may be formed of the human 

 jQieleton. The other parts of which our bodies are compof- 

 ed fhall be mentioned in the fame curfory manner. 



The mufcular part of the human fabric conlifts of numer- 

 ous bundles of flefliy fibres. Each bundle or diftincl mufcle, 

 is inclofed in a cellular membrane, by which means they 

 may be raifed, or feparated from one another by the hand 

 of the anatomift. They are inferted^ by ftrong tendinous ex- 

 tremities, into the different bones of which the fkeleton is 

 compofed, and, by their contraftion and difteniion, give rife 

 to all the movements of the body. The mufclesj therefore, 

 may be confidered as fo many cords attached to the bones ; 

 and Nature has fixed them according to the moft perfecSl 

 principles of mechanifm, fo as to produce the fitteft motions 

 in the bones or parts for the movement of which they are 

 intended. 



Tl^e heart is a hollow mufcular organ of a conical fhape, 

 and confifts of four diflincSl cavities. The two largeft are 

 called ventricles, and the two fmalleft auricles. The heart is 

 inclofed in the pericardium, a membranous bag, which like- 

 wife contains a quantity of water, or lymph. This water lu- 

 bricates the heart, and facilitates all its motions. The heart 

 is the general refervoir of the blood. By the contra(Stions 

 and dilations of this mufcle, the blood is alternately thrown 

 out of, and received into, its feveral cavities. When the 

 heart contracts, the blood is propelled from the right ventri- 

 cle into the lungs through the pulmonary arteries, which, 

 like all the other arteries, are furniflied with valves that play 

 eafily forward, but admit not the blood to regurgitate toward 

 the heart. The blood, after circulating through the lungs, 

 returns into the left ventricle of the heart by the pulmonary 

 vein. At the fame inflant, the left ventricle drives the blood 

 into the aorta, a large artery which fends off branches to 

 fupply the head and arms. Another large branch of the 



