

ABSORPTION OP THE DIGESTED FOOD. 353 



Acid potassium sulphate = 2.3 Magnesium sulphate .. . = n 7 



Sodium chlond = 4 . 3 Potassium sulphate = 12.0 



Sugar = 7.1 Sulphuric acid = T.Q 



Sodium sulphate = n.6 Potassium hydrate = 215.0 



The amount of the substance passing through the membrane into the water 

 of the cylinder within an equal time is proportional to the degree of concentra- 

 tion of the solution. If, therefore, the water within the cylinder is frequently 

 renewed, the course of the endosmotic equalization is the more rapid. Further, 

 the larger the pores of the membrane and the smaller the molecules of the sub- 

 stance in solution, the more quickly endosmosis takes place. It thus results 

 that the rapidity with which endosmosis takes place varies for different substances. 

 Thus the rapidity for sugar, sodium sulphate, sodium chlorid and urea is, as 

 i : i.i : 5 : 9.5. 



The endosmotic equivalent for each substance, however, is not constant. 

 It is influenced by: i. The temperature, with increase in which, in general, the 

 endosmotic equivalent increases. 2. C. Ludwig and Cloetta have demonstrated 

 that the endosmotic equivalent varies with the degree of concentration of the 

 penetrating solutions; it is larger for dilute solutions of substances. 



Should a solution of another substance be present in the cylinder instead of 

 water, an endosmotic current takes place from both sides, until complete equaliza- 

 tion is effected. In this process it is seen that these counter-currents of concen- 

 trated solutions have a disturbing influence on each other. If, however, two sub- 

 stances in, solution are present in the flask at the same time, both diffuse 

 toward the water, without interfering with each other. 3. The endosmotic 

 equivalent varies with the employment of different membranes of different porosity. 

 Sodium chlorid, which has an endosmotic equivalent of 4.3 when pig's bladder is 

 used, possesses an equivalent of 6.4 when a cow's bladder is employed; 2.9 

 with a swimming-bladder, and 20.2 with a collodion membrane. 



There are a number of fluids that, on account of the considerable size of their 

 molecules, are capable of passing with difficulty, if at all, through the pores of a 

 membrane impregnated with gelatinous substances, diffusible with difficulty. 

 These consist in part of fluids that contain substances, not in true solution, but 

 in a greatly diluted state of imbibition. Among such substances are the liquid 

 albuminates, solutions of starch, dextrin, gum, mucus and gelatin. They are 

 capable of gradually passing over into and mixing with other fluids by diffusion, 

 in the absence of an intervening porous membrane-wall ; they pass by endosmosis 

 with difficulty, if at all, through the pores of membranes impregnated with gelatin. 

 Nevertheless, the nature of the outside liquid must be taken into consideration; 

 egg-albumin, it is true, passes through membranes into salt-solutions, but not into 

 water; the transudate, under such conditions, becomes more concentrated. 

 Graham has designated the substances in question colloids, because in consider- 

 able concentration they become gelatinous. They also possess the property 

 of not crystallizing, as a rule, while crystalline substances, designated crystalloids, 

 are exchanged by endosmosis. The endosmotic apparatus thus constitutes a 

 mechanism for effecting a separation from mixtures of crystalloids and colloids, 

 which by Graham is designated dialysis. If mineral salts are added to the colloid 

 substances, their ability to pass through membranes is increased. 



That endosmosis takes place within the alimentary canal, through 

 its mucous membrane and the delicate membranes of the capillary 

 blood-vessels and lymphatics, cannot be denied. On the one side of 

 the membrane, within the tract, there are relatively concentrated aque- 

 ous solutions of salts, sugar, soaps, and peptones, all of which possess 

 slight diosmotic power. On the inner side of the vessels is the colloid, 

 albuminous solution of the blood and the lymph, practically incapable 

 of osmosis, and deficient in the matters in solution within the ali- 

 mentary canal, particularly in the state of hunger. The vital proper- 

 ties, however, probably in consequence of the motility of the proto- 

 plasmic structure within the membranes, also appear to exert some 

 influence upon endosmosis. Thus, Reid observed that the exfoliated 

 frog's skin is less permeable than living skin, and the latter, in turn, 

 more so after irritation had been applied. 

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