10 Absobption of Liquids by Animal Tissues 



by this means, to arrive at more definite conclusions concerning the effect of osmotic 

 pressure. In calculating the strength of a solution which shall be isosmotic with a 

 known solution, it is necessary only to make use of the simple formula: 



V = r>^oi> /I ■ / ?^;^ — ^ in which 



^ 22.35 (1 + (n — 1) a) 



P = osmotic pressure of known solution. 



y = strength of unknown solution in terms of normal solution. 



w = w, 2n, 3m, etc., according to basicity of salt. 



w= number of ions into which the molecule of salt is dissociated. 



a = degree of dissociation of solution of same molar concentration as known solution. 



After remaining in such solutions for intervals of one, three, six, and twenty-four 

 hours, the muscle is taken out, carefully dried, as before, and weighed. In the drying 

 of the muscle with filter paper, two errors are prone to creep into the work and should 

 be guarded against. The first of these is a positive one and consists in not removing 

 all of the fluid adhering to the surface. The second is a negative one and consists in 

 exerting undue pressure on the muscle, thereby drying out the surface layer of muscle, 

 and causing an increase of pressure upon the inner layers. This latter error is 

 greater, of course, the smaller the muscle, inasmuch as we have a much larger surface 

 in proportion to the total mass of muscle. The percentage gain or loss in weight of the 

 muscle (as ascertained by comparing the weight before immersion in the solution, 

 with the weight after removal from the same solution), gives the absorption. In the 

 experiments detailed here the gain or loss is interpreted as meaning an increase or 

 decrease in the amount of water in the muscle, although it is more than probable that 

 the change is due to interchange of ions through the sarcolemma and an ultimate 

 establishment of equilibrium between partial osmotic pressures on both sides of this 

 membrane. 



V. EFFECTS OF NON-ELECTROLYTES 



We understand by non-electrolyte any substance which exists in solution in the 

 molecular and not in the ionic form. Such substances, when in solution, do not con- 

 duct electricity and do not show irregularities in lowering of the vapor tension of the 

 solution. They obey the laws of osmotic pressure, however, and therefore give us 

 opportunity of studying the osmotic effects in absorption phenomena, although the 

 ionic effects are excluded by their use. The nonelectrolytes used in these experiments 

 were water, cane sugar, and urea. The concentrations were, except naturally in case 

 of water, made isosmotic with the various NaCl solutions to be used later. 



a. Absorption from Redistilled Water. — A gastrocnemius muscle placed in 

 redistilled water goes through the following phases of absorption: 



These results show, beyond a doubt, that in this case we are dealing with a 

 purely osmotic phenomenon. The natural result of placing a solution of salts (the 



112 



