THE LYMPHATIC SYSTEM. 313 



imbibed fluid penetrates the membrane by a kind of chemical 

 combination, and unites intimately with the substance of which its 

 tissues are composed. 



It is in this way that all imbibition and transudation take place 

 in the living body. Under the most ordinary conditions, the transu- 

 dation of certain fluids is accomplished with great rapidity. It has 

 been shown by M. Gosselin, 1 that if a watery solution of iodide of 

 potassium be dropped upon the cornea of a living rabbit, the 

 iodine passes into the cornea, aqueous humor, iris, lens, sclerotic 

 and vitreous body, in the course of eleven minutes; and that it 

 will penetrate through the cornea into the aqueous humor in three 

 minutes, and into the substance of the cornea in a minute and a 

 half. In these experiments it was evident that the iodine actually 

 passed into the deeper portions of the eye by simple endosmosis, 

 and was not transported by the vessels of the general circulation ; 

 since no trace of it could be found in the tissues of the opposite 

 eye, examined at the same time. 



The same observer showed that the active principle of belladonna 

 penetrates the tissues of the eyeball in a similar manner. M. Gos- 

 selin applied a solution of sulphate of atropine to both eyes of two 

 rabbits. Half an hour afterward, the pupils were dilated. Three 

 quarters of an hour later, the aqueous humor was collected by 

 puncturing the cornea with a trocar; and this aqueous humor, 

 dropped upon the eye of a cat, produced dilatation and immobility 

 of the pupil in half an hour. These facts show that the aqueous 

 humor of the affected eye actually contains atropine, which it 

 absorbs from without through the cornea, and this atropine then 

 acts directly and locally upon the muscular fibres of the iris. 



But in all the vascular organs, the processes of endosmosis and 

 exosmosis are very much accelerated by two important conditions, 

 viz., first, the movement of the blood in circulating through the 

 vessels, and secondly the minute dissemination and distribution of 

 these vessels through the tissue of the organs. 



The movement of a fluid in a continuous current always favors 

 endosmosis through the membrane with which it is in contact. For 

 if the two liquids be stationary, on the opposite sides of an animal 

 membrane, as soon as endosmosis commences they begin to ap- 

 proximate in constitution to each other by mutual admixture ; and, 

 as this admixture goes on, endosmosis of course becomes less active, 



1 Gazette Hebdomad aire, Sept. 7, 1855. 



