BOOK VIII. 



OF THE CIRCULATORY SYSTEM. 



PART I- 



Of the General Anatomy of the Circulatory System. 



CHAPTER I. 



GENERAL CONSIDERATIONS, 



THE Circulatory or th Vascular System* consists in a conge- 

 ries of tubes, or cylindrical canals, which convey the blood to 

 and from every part of an animal body, and therefore, enter into 

 the texture or composition of almost every portion of it. In all 

 animals there seems to be a necessity for the alternate reception 

 and discharge of alimentary materials; in the higher orders, this 

 is effected through the agency of the vascular system; but in the 

 most simple animals this system does not exist, and their whole 

 fabric being soft and permeable> nutritious matter is introduced 

 by a direct absorption, or a species of capillary attraction, after 

 the manner of a sponge, or any other porous body, and is dis- 

 charged by a process equally simple.* It is probable that there 

 are some parts of the human body whose mode of nutrition is 

 analogous to the latter ; as, for example, the articular cartilages, 

 the hair, nails, and so on ; for many observations tend to prove 

 that all these organs have an interstitial circulation. 



* Hunter on the blood. B^clard, Anat. Gen. 



