OF THE ERECTILE TISSUE. 269. 



other organs, vessels, which transport from the surfaces into 

 all parts of the mass, and hence back to the surfaces, the mat- 

 ters of absorption and secretion. In certain animals provided 

 with vessels, among which is man, their number is so great, 

 that they seem to occupy and form the whole mass of the 

 body. But, besides the above considerations, which are de- 

 rived from analogy, the arguments derived from inspection 

 also show that the vessels only traverse the mass of the body, 

 and do not constitute it. Observation also shows that, what- 

 ever may be the tenuity or softness of the last capillary ves- 

 sels, the arteries and veins form continuous canals. 



Observation teaches us, that new substances enter into the 

 vessels, and that others also unceasingly issue from them. 

 But this two-fold passage takes place in the finest parts of the 

 vessels, and by paths invisible even with the best optical in- 

 struments; the substances themselves circulate through these 

 passages in a state of division, in vapour, which eludes the 

 senses, and is imperceptible with the best microscopes. This* 

 passage, whether it occurs from without inward, or from with- 

 in outward, in extrinsic absorptions and secretions, or whether 

 it takes place in the closed cavities of the body, always ap- 

 pears to be performed through the intervention of the solid 

 and permeable substance of the body; that is to say, of the 

 substance called cellular, which, by imbibing, transmits in- 

 wards or outwards the inhaled or exhaled molecules. 



The same appears to be the case with respect to nutrition. 

 The vessels deposit and take up under the form of vapour, 

 and by invisible passages, in the cellular substance, the mole- 

 cules of the composition and decomposition of the organs. 



But all these phenomena, which are apparently physical, are 

 modified by the organized and living body in which they oc- 

 cur. It is especially to the unknown cause of these pheno- 

 mena, that the name of vital power has been given, or more 

 particularly, that of power of formation. 



II. OF THE ERECTILE TISSUE. 



396. The erectile, cavernous or spongy tissue, consists 

 of terminations of blood vessels, and especially of the radicles 



