114 NATURAL THEOLOar. 



proved by the single observation, that we cannot prick the 

 point of a pin into the flesh vs^ithout drawing blood, that iS; 

 without findmg a bloodvessel. Nor, internally, is their diffu- 

 sion less universal. Bloodvessels run along the surface of 

 membranes, pervade the substance of muscles, penetrate the 

 bones. Even into every tooth, we trace> through a small 

 hole in the root, an artery to feed the bone, as well as a vein 

 to bring back the spare blood from it ; both which, with the 

 addition of an accompanying nerve, form a thread only a 

 little thicker than a horsehair. 



Wherefore, when the nourishment taken in at the mouth 

 has once reached and mixed itself with the blood, every part 

 of the body is in the way of being supphed with it. And 

 this introduces another grand topic, namely, the manner in 

 which the aliment gets into the blood ; which is a subject 

 distinct from the preceding, and brings us to the considera- 

 tion of another entire system of vessels. 



III. For this necessary part of the animal economy, an 

 apparatus is provided in a great measure capable of being 

 what anatomists call demonstrated, that is, shown in the 

 dead body ; and a line or course of conveyance, which wo 

 can pursue by our examinations. 



First, the food descends by a wide passage into the intes- 

 tines, undergoing two great preparations on its way : one in 

 the mouth, by mastication and moisture — can it be doubted 

 with what design the teeth were placed in the road to the 

 stomach, or that there was choice in fixing them in this sit- 

 uation ? — the other by digestion in the stomach itself Of 

 this last surprising dissolution I say nothing, because it is 

 chemistry, and I am endeavoring to display mechanism. 

 The figure and position of the stomach — I speak all along 

 with a reference to the human organ — are calculated for 

 detaining the food long enough for the action of its digestive 

 juice. It has the shape of the pouch of a bagpipe ; lies 

 across the body ; and the pylorus, or passage by which the 

 food leaves it, is somewhat higher in the body than the car- 



