TRANSUDATION THROUGH ANIMAL TISSUES. 363 



COMPARATIVE INTENSITY OF ENDOSMOSIS OF WATER TOWARD DIFFERENT LIQUIDS, AS 

 MEASURED BY THE RISE OF THE COLUMN IN THE ExDOSMOMETER. 

 Endosmosis of water toward Divisions of the Endosmometer tube. 



Solution of gelatine ...... 3 



" gum 5 



" sugar . . . . . ]1 

 " albumen 12 



The primary cause of this variation in the phenomena of endosmosis 

 is the different absorptive power possessed by an animal membrane or 

 tissue for different liquids. This is partly shown by the experiments 

 of Chevreuil, in which oily matters were usually absorbed less readily 

 than either water or saline solutions. Nearly all animal membranes 

 also absorb water more rapidly than a solution of salt. If a membrane, 

 partly dried, be placed in a saturated solution of sodium chloride, it 

 will absorb the water in so much larger proportion than the salt that a 

 part of the salt will be left behind and deposited in a crystalline form 

 on the surface of the membrane. 



When an animal membrane, accordingly, is placed in contact with 

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

 the other ; and if that which is absorbed in the greatest quantity is also 

 readily diffused into the liquid on the opposite side, a rapid endosmosis 

 will take place in that direction, and a slow exosmosis in the other. 

 Consequent!}', the least absorbable fluid increases in volume by the con- 

 stant admixture of that which is taken up more rapidly. There are 

 even some cases in which endosmosis takes place without being accom- 

 panied by exosmosis. This occurs when water and albumen are em- 

 ployed as the two liquids. For while water readily passes inward 

 through the animal membrane, the albumen does not pass out. If an 

 opening be made in the large end of a fowl's egg, so as to expose the 

 shell-membrane, and the whole be then immersed in a goblet of water, 

 endosmosis will take place freely from the water to the albumen, so as 

 to distend the shell-membrane and make it protrude, like a hernia, from 

 the opening in the shell. But the albumen does not pass outward 

 through the membrane, and the water in the goblet remains pure. 

 After a time the pressure from within, due to the accumulation of fluid, 

 becomes so great as to burst the shell-membrane, after which the two 

 fluids mix uniformly with each other. 



But a substance like albumen, which will not pass out by exosmosis 

 toward pure water, may traverse a membrane which is in contact with 

 a solution of salt. This has been shown to be the case with the shell- 

 membrane of the fowl's egg, which, if immersed in a watery solution 

 containing from 3 to 4 per cent, of sodium chloride, will allow the escape 

 of a small proportion of albumen. Furthermore, if a mixed solution of 

 albumen and salt be placed in a dialysing apparatus, the salt alone will 

 at first pass outward leaving the albumen ; but after the exterior liquid 

 has become perceptibly saline, the albumen also begins to pass in appre- 

 ciable quantity. 



UULU 



