312 IMBIBITION AND EXHALATION. 



Beside, the power of absorption of an animal membrane is dif- 

 ferent for different liquids. Nearly all animal membranes absorb 

 pure water more freely than a solution of salt. If a membrane, 

 partly dried, be placed in a saturated saline solution, it will absorb 

 the water in larger proportion than the salt, and a part of the salt 

 will, therefore, be deposited in the form of crystals on the surface 

 of the membrane. 



Oily matters, on the other hand, are usually absorbed less readily 

 than either water or saline solutions. 



Chevreuil has investigated the absorbent power of different 

 animal substances for different liquids, by taking definite quanti- 

 ties of the animal substance and immersing it for twenty-four 

 hours in different liquids. At the end of that time, the substance 

 was removed and weighed. Its increase in weight showed the 

 quantity of liquid which it had absorbed. The results which were 

 obtained are given in the following table : l 



100 PARTS OP WATER. SALINE SOLUTION. OIL. 



Cartilage, 



Tendon, 



Elastic ligament, 



Cornea, 



Cartilaginous ligament, 



Dried fibrin, 



absorb in 

 24 hours, 



f 231 parts. 125 parts. 



178 " 114 " 8. 6 parts. 



148 " 30 " 7.2 



461 " 370 " 9.1 " 



319 " 3.2 " 



I 301 " 154 " 



The same substance, therefore, will take up different quantities 

 of water, saline solutions, and oil. 



Accordingly, when an animal membrane is placed in contact 

 with two different liquids, it absorbs one of them more abundantly 

 than the other ; and that which is absorbed in the greatest quantity 

 is also diffused most abundantly into the liquid on the opposite side 

 of the membrane. A rapid endosmosis takes place in one direc- 

 tion, and a slow exosmosis in the other. Consequently, the least 

 absorbable fluid increases in volume by the constant admixture of 

 that which is taken up more rapidly. 



The process of endosmosis, therefore, is essentially one of im- 

 bibition or absorption of the liquid by an animal membrane, com- 

 posed of organic ingredients. We have already shown, in de- 

 scribing the organic proximate principles in a previous chapter, 

 that these substances have the power of absorbing watery and 

 serous fluids in a peculiar way. In endosmosis, accordingly, the 



1 In Longet's Traite de Physiologic, vol. i. p. 383. 



