OF THE VESSELS IN GENERAL. 239 



name of vascular system with black blood, and that mentioned 

 in the second place, under the name of vascular system with 

 red blood. It is easy to perceive that this division, pregnant 

 with practical results, is entirely founded on a physiological 

 basis, and not on the resemblance of the texture of the parts. 



351. The three species of vessels having a very great ana- 

 logy with each other; the two sanguineous vascular systems 

 having especially great relation with each other; and the 

 venous and lymphatic systems also greatly resembling each 

 other, we must, before describing each species, present the ge- 

 neral considerations just alluded to, those which relate to the 

 vessels generally, as well as those which refer to their termi- 

 nations. 



SECTION I. 



ARTICLE I. 

 OF THE VESSELS IN GENERAL. 



352. The situation of the vessels is interior or deep seated. 

 The largest are generally placed towards the centre of the 

 body, and at the surface very small ones only are found, and 

 even in this case, they are separated from external bodies by 

 a layer of substance which is not vascular. 



The principal vessels, either in the trunk or in the limbs, 

 are generally placed in the same directions as that of the 

 flexion of the parts. We generally find together an artery, 

 one or two veins, and several lymphatic vessels: besides, we 

 meet with many lymphatic vessels and veins under the skin, 

 and but few arteries. 



353. The respective volume of the three kinds of vessels 

 is such, generally, that the vessels which return the fluids, 

 that is to say, the veins and lymphatics, are, taken as a whole, 

 much more voluminous than the arteries. The veins alone 



are generally much more capacious than the arteries to which 

 32 



