PHYSIOLOGY OF THE CIRCULATION. 115 



the diameter of the latter, and thus increasing the 

 velocity of the currents of blood, it also adds in- 

 directly to their absorbing power. 



I have made no mention of the manner in which 

 absorption might be supposed to be effected by the 

 lacteals and lymphatics, because it appears to me 

 very doubtful whether those vessels really possess 

 any active absorbing power of their own. On the 

 contrary, the information already possessed on the 

 subject of absorption, the intimate connection shown 

 to exist between the rapidity of the circulation of 

 the blood and the activity of the absorbing process, 

 the dependence of the latter on the former action, 

 and the absence of any adequate mechanism in the 

 so-called absorbent vessels, all tend to invest with 

 probability the opinion which was, I believe, first 

 advanced by my friend Mr. Fenwick* viz., that the 

 substances contained in these vessels are derived 

 from the adjacent blood-vessels by a process of 

 effusion analogous to secretion. 



It might to some appear improbable, that in a 

 system of continuous tubes like the blood-vessels, 

 through the walls of which, in the earlier part of 

 their course, effusion has been shown to occur, the 

 opposite process of absorption should nevertheless 

 be enabled to proceed throughout the rest of their 

 extent. To meet this difficulty, I may briefly relate 

 three experiments one performed with a rigid, 

 another with an elastic and yielding, and the third 

 with a membranous tube in order to show that, 



* " Medical Gazette," July 21st, 1843, vol. xxxii. p. r.05. 



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