EFFECTS OF PRESSURE ON THE MUSCLES. 291 



kinds are constantly performing their opposite functions. 

 The flesh, and all the other parts of the body, are formed 

 by the secretory system, which consists of the fine ex- 

 tremities of the arteries. We have already explained 

 the manner in which the food is converted into chyle by 

 the process of digestion, and now this is conveyed into 

 the circulation, to be converted into blood. Now it is 

 from the blood thus formed, that the secreting vessels 

 produce all the different kinds of substance of which the 

 several parts of the animal system are composed, one 

 division forming flesh, another cartilage, and another 

 bone, &c. All the fluids are also formed by appropriate 

 organs belonging to the same system. Thus one set 

 produce tears, another saliva, and another bile, and 

 soon. 



On the contrary, the absorbent system takes up, and 

 conveys from one part to another, the various fluids 

 which are either employed in the process of secretion, 

 or which being secreted in some cavity, or on some in- 

 ternal surface, and having performed its office, is to be 

 conveyed out of the body. Thus, the absorbents suck 

 up the chyle by millions of mouths, and carry it to the 

 thoracic duct, through which it is delivered into the cir- 

 culation. They also absorb the superabundant moisture 

 which is secreted in every interior part of the body, and 

 consequently, did they cease to act, this watery fluid 

 would accumulate, and a universal dropsy would en- 

 sue. This disease, as it occurs, is owing to the defi- 

 cient action of the absorbents. 



It is the o'ffice therefore of the secreting system, to 

 produce and deposite the matter composing all the dif- 

 ferent organs, and fluids of the body ; while the absor- 

 bents in their turn, take up and carry away, by slow, 

 and insensible degrees, the matter thus deposited. 



Such being the appropriate functions of these two 

 great systems of vessels, which are distributed to every 

 part of the animal frame, it is plain that the identical 

 particles of which we are composed, are perpetually 

 changing, and that in this respect we are not the same 

 individuals now that we were formerly, nor will our bod- 

 ies at a future time, contain a particle of the identical 

 matter which they do at this moment, 



