THE LYMPHATIC SYSTEM. 315 



the extent of surface over which the two liquids come in contact 

 with the intervening membrane. It is very evident, therefore, that 

 it will be very much facilitated by the anatomical distribution of 

 the capillary bloodvessels. 



It is in some of the glandular organs, however, that the transu- 

 dation of fluids can be shown to take place with the greatest rapi- 

 dity. For in these organs the exhaling and absorbing surfaces are 

 arranged in the form of minute ramifying tubes and follicles, which 

 penetrate everywhere through the glandular substance ; while the 

 capillary bloodvessels form an equally complicated and abundant 

 network, situated between the adjacent follicles and ducts. In this 

 way, the union and interlacement of the glandular membrane, on 

 the one hand, and the bloodvessels on the other, become exceed- 

 ingly intricate and extensive ; and the ingredients of the blood are 

 almost instantaneously subjected, over a very large surface, to the 

 influence of the glandular membrane. 



The rapidity of transudation through the glandular membranes 

 has been shown in a very striking manner by Bernard. 1 This ob- 

 server injected a solution of iodide of potassium into the dnct of 

 the parotid gland on the right side, in a living dog, and immediately 

 afterward found iodine to be present in the saliva of the correspond- 

 ing gland on the opposite side. In the few instants, therefore, re- 

 quired to perform the experiment, the salt of iodine must have 

 been taken up by the glandular tissue on one side, carried by the 

 blood of the general circulation to the opposite gland, and there 

 transuded through the secreting membrane. 



We have also found the transudation of iodine through the 

 glandular tissue to be exceedingly rapid, by the following experi- 

 ment. The parotid duct was exposed and opened, upon one side, 

 in a living dog, and a canula inserted into it, and secured by liga- 

 ture. The secretion of the parotid saliva was then excited, by in- 

 troducing a little vinegar into the mouth of the animal, and the 

 saliva, thus obtained, found to be entirely destitute of iodine. A 

 solution of iodide of potassium being then injected into the jugu- 

 lar vein, and the parotid secretion again immediately excited by 

 the introduction of vinegar, as before, the saliva first discharged 

 from the canula showed evident traces of iodine, by striking a blue 

 color on the addition of starch and nitric acid. 



The processes of exosmosis and endosmosis, therefore, in the living 



1 Lemons de Physiologie Exp&imentale, Paris, 1856, p. 107. 



