NATURE OF PROTEIN SOLUTIONS 341 



which is involved in the transformation, the other the work per- 

 formed in bringing the molecule to the pressure of the system (56) ; 

 the latter factor is, of course, dependent upon the concentration of 

 the substances within the system, while the former, equally 

 obviously, is not. If the reacting components in a system exerted 

 no osmotic pressure whatever, the expression for the work done in 

 the transformation of a given mass of the components would, 

 therefore, be a constant one (depending only upon temperature), 

 and, consequently, at any stage of the reaction the work done in 

 transforming unit mass would be the same, whatever the concen- 

 tration of the reacting components. Under these conditions the 

 reaction would always proceed to an end in one direction or the 

 opposite; since the work performed at every stage of the reaction 

 would be unaffected by the concentration of the reacting com- 

 ponents. Now it has been shown that the reactions between 

 toxins and anti-toxins, lysins, and anti-lysins, etc., attain definite 

 equilibria (3) and hence these bodies must, in solution, exert 

 definite osmotic pressure. The probable protein nature of these 

 bodies has been commented upon in a previous chapter (Chap. 

 VII, section 7). Moreover, it has been shown that a definite 

 equilibrium is attained between proteins and the antibodies which 

 are produced in the serum when these proteins are injected into 

 the circulation (3), and definite equilibria are attained between 

 different proteins in solution (121) and between proteins and in- 

 organic acids and bases (Cf. Chap. IX) and in protein digests (122) 

 (123) (99) (102) (107). Many of these equilibria, it has been 

 shown, can be approached from either direction, so that they are 

 not " false" equilibria (27) attributable to the internal molecular 

 friction or hysteresis of the systems. We may, therefore, safely 

 conclude that in many instances, and especially in the form of 

 their salts, proteins and bodies allied to proteins exert, when in 

 solution, definite osmotic pressures; and are distributed in molec- 

 ular dispersion throughout their solutions in accordance with the 

 law of Avogadro. 



It is, of course, not for a moment contended that this is the case 

 in every apparent "solution" of protein. Proteins, like other 

 bodies, and more easily than the majority of crystalloids, can also 

 be obtained in a suspended condition. Under such circumstances 

 they may form apparently stable suspensions, simulating true 

 solutions in certain respects. An illustration of such suspension 



