i 3 4 SCIENCE PROGRESS 



sulphate concentration, and definite hydrogen-ion concentration (which is de- 

 termined by the fourth component), the system is completely determined. 



Another difficulty in the application of the phase-rule to emulsoids consisted 

 in the fact that the equilibrium condition seemed to be dependent on the original 

 protein concentration. For example, Chick and Martin {Bioch. Journ. vol. 7, 

 p. 380, 1913) find that egg-albumen is more completely precipitated the greater 

 the original concentration. The error committed by Chick and Martin lies in 

 assuming that the ratio between ammonium sulphate and water is not altered 

 during the precipitation, and therefore they carried out no determinations of 

 ammonium sulphate in the filtrate From Sorensen's experiments it is evident 

 water-containing egg-albumen is precipitated, so that the ratio between ammonium 

 sulphate and water is different in the filtrate from that in the original mixture. 

 It is clear that the greater the original concentration of egg-albumen, the more 

 water will be taken away from the solution, and, consequently, the greater the 

 concentration of ammonium sulphate will become in the filtrate, and, as an 

 increase in the ammonium sulphate concentration brings about greater com- 

 pleteness in the precipitation of egg-albumen, the experiments of Chick and 

 Martin are quite in accordance with the phase-rule. 



Thus, Sorensen, who in his proof of the applicability of the phase-rule to emulsoid 

 systems gives many interesting details which space does not permit one to 

 deal with, has justified his contention that the study of colloids is best promoted 

 by applying the same principles and points of view as are used in the study of 

 true solutions. This is, perhaps, still more brought out in the last chapter of his 

 book, which contains what is probably an epoch-making treatment of the osmotic 

 pressure of emulsoids. 



For the first time this much-disputed question is made clear. It is found that 

 an egg-albumen solution of a given composition has a constant well-defined 

 osmotic pressure the magnitude of which is dependent on the egg-albumen 

 concentration, the ammonium sulphate concentration, and the hydrogen-ion con- 

 centration, and varies with these factors according to definite laws. Consequently 

 the osmotic pressure of a correctly defined egg-albumen solution is as definite a 

 quantity as the osmotic pressure of a crystalloidal solution of definite composition. 



In this review it has only been possible to deal with a few isolated questions, 

 and the scope and beautiful exactness of the work can only be appreciated by a 

 detailed perusal of the book. The same holds for the masterly mathematical 

 treatment, for example, of amphoteric electrolytes and the application of Donnan's 

 formulae to the case of albumen solutions. It is clear that these researches form 

 the beginning of a new era in colloid chemistry, and their stimulating influence on 

 all biological sciences cannot as yet be estimated, but must, at any rate, be 

 profound. Similarly, one may perhaps expect that this change of outlook in 

 colloid chemistry will lead agriculturalists and soil chemists to occupy themselves 

 with the emulsoids of the soil. 



MECHANISM AND VITALISM, by Joshua C. Gregory, B.Sc, 

 F.I.C. : on The Organism as a Whole, from a Physicochemical View- 

 point. By Jacques Loeb, M.D., Ph.D., Sc.D. [Pp. viii + 379, 

 with 51 illustrations.] (New York and London: G. P. Putnam's Sons, 

 19 1 6. Price 12s. 6d. net.) 



In his Zoonomia Erasmus Darwin warns inquirers into diseases that "animation" 

 includes more than mechanism and chemistry. This warning clearly and simply 



