REVIEWS 503 



"From the point of view of the physicist, a theory of matter is a policy 

 rather than a creed ; its object is to connect or co-ordinate apparently diverse 

 phenomena, and above all to suggest, stimulate, and direct experiment. It ought 

 to furnish a compass which, if followed, will lead the observer farther and farther 

 into previously unexplored regions. Whether these regions will be barren or 

 fertile, experience alone will decide ; but, at any rate, one who is guided in this 

 way will travel onward in a definite direction, and will not wander aimlessly to 

 and fro." 



Prof. Brailsford Robertson has written a book in which the guiding theory or 

 "policy" is the applicability of the laws of homogeneous solutions (the law of mass 

 action, and the theory of electrolytic dissociation), to the chemical and physical 

 behaviour of that wide and complex group of substances known as the proteins. 

 It is a remarkable attempt at relatively simple generalisation of complex, and 

 indeed apparently conflicting, facts and observations. There is probably no 

 subject which has furnished a greater number of difficulties from the theoretical 

 point of view. Whether Prof. Robertson has unduly simplified the basis of the 

 theoretical treatment has yet to be seen. What he most certainly has done is to 

 bring order out of chaos and regularity out of confusion. That, indeed, is the 

 great and outstanding merit of the treatment which the subject has received at 

 his hands. 



Briefly, Prof. Robertson's thesis is that the proteins are essentially electrolytes, 

 and behave like other electrolytes, due regard being paid to the kind of ionisation 

 of which the protein molecule is capable. The fundamental concept has to do 

 with the grouping - N . HO . C - in the protein molecule. The kind of change 

 which, on Robertson's view, takes place may be illustrated by the action of an 

 alkali and an acid respectively, viz. : 



and 



That is, in both cases two divalent complex ions are produced by the rupture of an 

 internal - NHOC - group. (Robertson points out that the end amino and 

 carboxyl groups cannot possibly account for the whole physicochemical behaviour 

 of the proteins.) 



Starting from this simple concept, we are led to a striking, and indeed con- 

 vincing, explanation of such problems as the electrochemical behaviour of the 

 proteins in general, the electrochemical equivalent, combining weight as distinct 

 from molecular weight, the magnitude of the velocity of the protein ions in a field 

 of force, the type of union of salts with proteins, e.g., the fact that the compounds 

 of the proteins with an acid or a base are good electrolytes, but do not give the 

 reaction of, say, chlorine ion or sodium ion, the fact that casein, for example, will 

 displace carbonic acid from its union with calcium hydroxide, the osmotic pressure 

 of protein-base compounds, the absence of hydrolytic dissociation of protein salts, 

 and other characteristics of these substances. 



A rough idea of the scope of the work is given by an enumeration of the 

 chapter headings : the chemical constitution of the proteins, the preparation of pure 

 proteins, quantitative estimation of the proteins, the compounds of the proteins 

 (four chapters), the formation and dissociation of protein salts, the combining 

 capacity of the proteins, the electrical conductivity of solutions of protein salts, the 



