314: IMBIBITION AND EXHALATION. 



and ceases entirely when the two liquids have become perfectly 

 alike in composition. But if one of the liquids be constantly 

 renewed by a continuous current, those portions of it which have 

 become contaminated are immediately carried away by the stream, 

 and replaced by fresh portions in a state of purity. Thus the 

 difference in constitution of the two liquids is preserved, and 

 transudation will continue to take place between them with una- 

 bated rapidity. 



Matteucci demonstrated the effect of a current in facilitating 

 endosmosis by attaching to the stopcock of a glass reservoir filled 

 with water, a portion of a vein also filled with water. The vein 

 was then immersed in a very dilute solution of hydrochloric acid. 

 So long as the water remained stationary in the vein it did not give 

 any indications of the presence of the acid, of did so only very 

 slowly ; but if a current were allowed to pass through the vein by 

 opening the stopcock of the reservoir, then the fluid running from 

 its extremity almost immediately showed an acid reaction. 



The same thing may be shown even more distinctly upon the 

 living animal. If a solution of the extract of nux vomica be in- 

 jected into the subcutaneous areolar tissue of the hind leg of two 

 rabbits, in one of which the bloodvessels of the extremity have 

 been left free, while in the other they have been previously tied, 

 so as to stop the circulation in that part in the first rabbit, the 

 poison will be absorbed and will produce convulsions and death in 

 the course of a few minutes; but in the second animal, owing to the 

 stoppage of the local circulation, absorption will be much retarded, 

 and the poison will find its way into the general circulation so 

 slowly, and in such small quantities, that its specific effects will show 

 themselves only at a late period, or even may not be produced at all. 



The anatomical arrangement of the bloodvessels and adjacent 

 tissues is the second important condition regulating endosmosis 

 and exosmosis. We have already seen that the network of capil- 

 lary bloodvessels results from the excessive division and ramifica- 

 tion of the smaller arteries. The blood, therefore, as it leaves the 

 arteries and enters the capillaries, is constantly divided into smaller 

 and more numerous currents, which are finally disseminated in the 

 most intricate manner throughout the substance of the organs and 

 tissues. Thus, the blood is brought into intimate contact with the 

 surrounding tissues, over a comparatively very large extent of sur- 

 face. It has already been stated, as the result of Dutrochet's inves- 

 tigations, that the activity of endosmosis is in direct proportion to 



