312 FUNCTIONS OF NUTRITION. 



ligature. To its top there is fitted a narrow upright glass tube, open 

 at both ends. The instrument thus prepared is filled with a saline or 

 organic solution and placed in distilled water ; so that the membrane, 

 stretched: over its mouth, shall be in contact with water on one side and 

 with the interior solution on the other. As the water then passes in 

 by endosmosis faster than the ingredients of the solution pass out, an 

 accumulation takes place within the vessel, and the fluid rises in the 

 upright tube. The height to which it thus rises in a given time is a 

 measure of the intensity of the endosmosis, and of its excess over 

 exosmosis. Such an instrument is called an endosmometer. 



Physical Conditions influencing Endosmosis. The conditions which 

 regulate the rapidity and extent of endosmosis have been investigated 

 by Dutrochet,* Graham, Yierordt, Matteucci, and Cima. The first of 

 these conditions is the freshness of the animal membrane. A mem- 

 brane which has been dried and remoistened, or which has lost its 

 freshness from any cause, will not produce its full effect. If the mem- 

 brane be allowed to remain and macerate in the fluids, the endosmotic 

 column, after rising to a certain height, begins to descend when putre- 

 faction commences, and the two liquids finally sink to the same level. 



The next condition is the extent of contact between the membrane 

 and the liquids. The greater this extent, the more rapid is endosmosis. 

 An endosmometer with a wide mouth will produce more effect than 

 with a narrow one, though the volume of liquid may be the same. 

 The action which takes place in the membrane is proportional to its 

 extent of surface. 



The nature of the membrane employed, and even its position in re- 

 gard to the two liquids, also influence the result. Different membranes 

 act with different degrees of force, since the power of absorption for 

 a given liquid varies with different tissues. In the experiments of 

 Chevreul,f definite quantities of various animal tissues were immersed 

 in different liquids for twenty-four hours ; at the end of which time 

 their increase in weight showed the quantity of liquid absorbed. The 

 result is given in the following table : 



COMPARATIVE POWER OF ABSORPTION IN DIFFERENT TISSUES. 

 100 Parts of Water. Saline Solution. Oil. 



Cartilage, 



Tendon, 



Elastic ligament, 



Cornea, 



Cartilaginous ligament, 



Dried fibrine, 



absorb in 

 24 hours, 



231 parts. 125 parts. 



178 

 148 

 461 

 319 

 301 



114 " 8.6 parts. 



30 7.2 " 

 370 " 9.1 " 



3.2 



151 



Thus the tissue of cartilage will absorb, weight for weight, nearly 

 30 per cent, more water than that of the tendons ; and the cornea will 

 absorb nearly twice as much as cartilage. The animal tissues in general 



* Nouvelles Recherches sur 1'Endosmose et 1'Exosmose. Paris, 1828. 

 f In Longet. Traite de Physiologic. Paris, 1861, tome i., p. 383. 



