IMBIBITION AND ENDOSMOSIS. 



293 



or exosmosis", of the albuminoid constituents of the blood. On the other 

 hand, there is a constant absorption of peptones, which are destined to be 

 converted into the albuminoid constituents of the blood. 



Recognizing the fact that albumen is capable of inducing a more power- 

 ful endosmotic current than almost any other liquid, it has been shown that 

 it never itself passes through membranes in the exosmotic current, but that 

 albuminoids, after transformation by digestion into peptones, or albumen 

 mixed with gastric juice, pass through animal membranes with great facility. 

 The experiments by which these facts are demonstrated are of the highest 

 physiological importance. On removing part of the shell of an egg, so as to 

 expose its membranes, and immersing it in pure water, the passage of water 

 into the egg is rendered evident by the projection of the distended mem- 

 branes ; but although the surrounding liquid becomes alkaline and the appro- 

 priate tests reveal the presence of some of the inorganic constituents of the 

 egg, the presence of albumen can not be detected. When the contents of the 

 egg are replaced by the serum of the blood, the same result follows. " After 

 six or eight hours of immersion, the serum had yielded to the water in the ves- 

 sel all its saline elements, chlorides, sulphates, phosphates, which were easily 

 recognized by their peculiar reactions, but not a trace of albumen " (Dutrochet). 



A very simple apparatus for illustrating endosmotic action can be con- 

 structed in the following way : Remove carefully a circular portion, about 

 an inch (25'4 mm.) in diameter, of the shell from one 

 end of an egg, which may be done without injuring the 

 membranes, by cracking the shell into small pieces, which 

 are picked off with forceps. A small, glass tube is then 

 introduced through an opening in the shell and mem- 

 branes of the other end of the egg, and is secured in a 

 vertical position by wax or plaster of Paris, the tube pene- 

 trating tho yelk. The egg is then placed in a wine-glass 

 partly filled with water. In the course of a few minutes 

 the water will have penetrated the exposed membrane, 

 and the yelk will rise in the tube. 



The force with which liquids pass through mem- 

 branes, called cndomostic or osmotic force, is to a great 

 degree dependent upon the influence of the membranes 

 themselves. This influence is always purely physical, in 

 experiments made out of the body ; and physiological ab- 

 sorption can be explained, to a certain extent, by the same 

 laws. It must be remembered, however, that the proper- 

 ties of organic structures, which are manifested only in 

 living bodies, are capable of modifying these physical phe- 

 nomena in a remarkable degree. For example, all living 

 tissues are capable of selecting and appropriating from 

 the nutritive fluids the materials necessary for their regeneration ; and the 

 secreting structures of glands also select from the blood certain constitutents 

 which are used in the formation of their secretions. These phenomena and 



FIG. 97. Egg prepared 

 so as to illustrate en- 

 dosmotic action. 



