240 GENERAL ANATOMY. 



they correspond; this holds good, particularly with respect 

 to the larger vessels of the body. As to the relation of volume 

 and number, or of the total capacity between the venous and 

 lymphatic vessels, it is less known; it is very well known, 

 however, that under the skin, the mucous membranes, and 

 around the sefous membranes, there are a great many veins and 

 lymphatic vessels; that in the muscular interstices of the limbs, 

 and of the parietes of the trunk, there are also numerous lym- 

 phatic vessels with the veins, while in the spinal canal, and 

 within the cranium there exists a great many voluminous 

 veins, and few or perhaps no lymphatic vessels. Do these re- 

 lations depend on the difference of the matter with which the 

 muscles and the nervous substance are nourished, and conse- 

 quently on the different matter which remains in the circula- 

 tion? 



354. The external form of the vascular system is that of a 

 tree, the trunk of which is attached to the heart, and which is 

 successively divided into branches, and ramusculi which be- 

 come smaller and smaller branches. Each part, from its origin 

 in a larger branch to its division in smaller ones, generally 

 preserves a cylindrical form. Each branch being smaller than 

 the one from which it proceeds, and larger than each of the 

 ramusculi arising from it, the result is a successive diminu- 

 tion from the trunk to the end of each of these last ramifica- 

 tions. Since, generally speaking, the sum of the branches re- 

 sulting from the division of a trunk, is greater than the volume 

 of the trunk itself, it follows, that the vascular system has the 

 form of a cone whose summit is at the heart, and whose base 

 is formed by the union of all the branches ramified in the body. 



355. The number of the divisions of the vascular system, 

 from its centre or origin, to its last sub-divisions, is not the 

 same in all its parts. It has been very much exaggerated in 

 computing it at forty; Haller was nearer to the truth, in consi- 

 dering the maximum of the successive divisions of a vessel 

 from its trunk to its last ramifications to be about twenty. 



In certain places vessels are divided, and form a bifurcation 

 in such a manner, that the trunk terminates by its division into 

 two branches, and the branch, by its separation, into two small 



