278 ABSORPTION AND SANGUIFICATION. 



musk, assafoetida, and saline compounds, they were seldom found in 

 the chyle, though many of them were detected in the blood and in the 

 urine. The colouring matter appeared to be seldom absorbed at all ; 

 the odorous substances were generally detected in the venous blood and 

 in the urine, but not in the chyle ; whilst, of the saline substances, 

 many were found in the blood and in the urine, and only a very few in 

 the chyle. 



491. This passage of substances in a state of perfect solution, from 

 the stomach into the blood-vessels, is probably due to the operation of 

 that peculiar modification of Capillary Attraction, which is called En- 

 dosmose. When two fluids differing in density are separated by a 

 thin animal or vegetable membrane, there is a tendency to mutual 

 admixture through the pores of the membrane; but the less dense 

 fluid will transude with much greater facility than the more dense ; 

 and consequently there will be a considerable increase on the side of 

 the denser fluid; whilst very little of this, in comparison, will have 

 passed towards the less dense. When one of the fluids is contained in 

 a. sac or cavity, the flow; of the other towards it is termed Endosmose, 

 or flow-inwards ; whilst the contrary current is termed Exosmose or 

 flow-outwards. Thus if the caecum of a fowl, filled with syrup or 

 gum-water, be tied to the end of a tube, and be immersed in pure 

 water, the latter will penetrate the caecum by Endosmose, and will so 

 increase the volume of its contents, as to cause the fluid to rise to a 

 considerable height in the attached tube. On the other hand, a small 

 proportion of the gum or syrup will find its way into- the surrounding 

 fluid by Exosmose. But if the caecum were filled with water, and 

 were immersed in a solution of gum or sugar, it would soon be nearly 

 emptied, the Exosmose being much stronger than the Endosmose. 

 It is in this manner that we may cause the flattened corpuscles of the 

 blood to be distended into spheres, by treating them with water; or 

 may .empty them almost completely, by immersing them in syrup 

 (215); since their contents are more dense than the surrounding 

 fluid in the ; first case, so. that they will be augmented by Endosmose; 

 whilst they are less dense in the second, so as to be diminished by 

 Exosmose. 



492. How it seems to be in this manner, that substances contained 

 in the cavity of the stomach, and perfectly dissolved by its fluids, are 

 received into the blood-vessels ; for as the blood is the fluid of greater 

 density, it will have a tendency to draw towards it, by Endosmose, 

 the saline and other matters, which are in a state of perfect solution 

 in the stomach. The Mucous membrane, which forms the inner wall 

 of that organ,- is most copiously supplied with blood-vessels; partly, 

 indeed, that they may afford the materials of the gastric secretion ; but 

 partly, also, that they may take up the substances, which are capable 

 of entering the circulating current by this direct channel. The move- 

 ment of blood through the vessels, tends to accelerate the permeation 

 of liquids through their walls, in a very remarkable degree : as may 

 be shown by the following simple experiment. If a membranous tube, 

 such as a piece of the small intestine or of a large vein of an animal, 

 be fixed by one extremity to an opening at the bottom of a vessel 



