TEXTURE OF THE VEINS. 171 



varieties are found, in their place and manner of origin, in posi- 

 tion, and in the number of their ramifications. They are com- 

 paratively rare in the trunks of the first order, more common in 

 those of tire second, and still more usual in those of the third and 

 fourth. From these causes, discrepancies are continually found 

 in the descriptions ^of the most approved authorities, and must 

 last so long as writers repose upon a partial experience, instead 

 of referring to what has been most generally observed. 



CHAPTER III. 



OF THE TEXTURE OF THE VEINS. 



THE veins, from their duty of receiving the blood in all parts 

 of the body from the extreme arteries, and returning it to the 

 heart, by successively collecting it into the two venae cavse, may 

 be. more appropriately compared to the roots of a tree, than to 

 its branches. The variations in them, as well as their anasto- 

 moses, are more frequent than in the arteries. 



They are more numerous than the arteries ; for, in addition 

 to two venous trunks attending each artery wherever the struc- 

 ture of the part is intended for locomotion, as in the extremi- 

 ties, and in some places upon the trunk of the body, there is a 

 very abundant class of veins which are superficial or subcuta- 

 neous, and which, when filled properly with injecting matter, 

 form a fine vascular network over the whole surface of the body.* 

 These superficial veins, in some places, form trunks even larger 

 than such as attend the arteries, and especially in the extremi- 

 ties. Besides the excess in number, the veins which attend the 

 arteries (Vence, Comites) have a capaciousness which, in many 

 cases, is double that of the latter. From these several circum- 

 stances, it results that the area of the venous system vastly ex- 

 ceeds that of the arterial. 



* Pawli Mascagni Anatoin, Univers. Pisis, 1823. 



