OP THE VESSELS IN GENERAL. 347 



alkaline solutions do not alter its form, and dissolve it very 

 little. 



The greater number of these anatomical, physical or chemi- 

 cal characters, are altogether the reverse of those of the liga- 

 mentous tissue, and different from those of the muscular fibre, 

 with which the elastic tissue has been very improperly con- 

 founded. It resembles, however, in some respects, the mus- 

 cular fibre, and seems to be of a nature intermediate between 

 this latter and the cellular and fibrous tissues. 



Its vital properties are very obscure, especially in the liga- 

 ments, and even in the larger vessels. Its functions depend on 

 its elasticity, which every way antagonises the action of gravi- 

 tation, or that of the muscles. 



362. The parietes of the vessels are themselves provided 

 with sanguineous and lymphatic vessels, vasa vasorum. The 

 former may be perceived in all the vessels which are not less 

 than half a line in diameter; but they can not be traced into 

 the thickness of the inner membrane. The lymphatics can 

 only be observed on the larger vessels. The vascular system 

 is also provided with nerves* furnished by the spinal marrow, 

 and by the great sympathetic, and which are distributed in the 

 external parts of their parietes. 



363. The vessels whose trunk, branches, and the principal 

 ramifications are placed in the common cellular tissue, after 

 having divided, penetrate into the mass of the organs, there 

 ramify to such an extent as to become invisible to the naked 

 eye, and terminate as we shall mention presently; but the dis- 

 tention of the vessels in the organs varies in several points 

 which it is necessary to treat of successively. 



364. Their origin is more or less distant from their termi- 

 nation, and consequently they have various lengths. Gene- 

 rally, vessels branch off from their trunk very near the organ 

 to which they are destined. When this is not the case, it is 

 owing to some local disposition. Thus the spermatic vessels 

 have their origin at a great distance from the organs in which 



* Wrisberg, de Nereis arteries venasque cornitantibus; in syllog. comm. 

 Getting. 1800. 



33 



