TROCEEDINGS OF SECTION D. 499 



These results, having regard to our initial supposition, that these 

 life-phenomena mainly depended upon the reactions and properties of the 

 iron-proteids in the tissues, tend to show that the reactions of the iron- 

 proteids are chemical reactions, that the iron-proteids are not, in fact, 

 merely instances of the increase in concentration of ions at the surface 

 of two phases, or merely instances of the physical retention of substances 

 owing to the co-efficient of partition between the solution and the pro- 

 teins of the cell favoring the proteins. Nor do these results lend 

 support to the idea that the ion-proteids are " absorptions compounds " 

 for, as we have seen, the temperature — co-efRcient for a typical case of 

 absorption-combination is only 1-36; on the contrary, the temperature 

 co-efficients quoted above are many of them abnormally high even for 

 chemical reactions. 



Summing up, therefore, the information regarding the physico- 

 chemical nature of the iron-proteid compounds which we have derived 

 from a consideration of the reactions towards electrolytes and temperature 

 of living tissues themselves, we find ourselves in possession of the 

 following facts : — 



1. That two types of ion-proteid compounds exist apart from those 

 which are insoluble, namely, that in which the ion, derived from the 

 external solution, is readily dissociable as such and is readily replaced 

 by other ions according to their relative masses, and that in which the 

 ion derived from the external solution is not dissociable as such, but is 

 bound up in a non-diffusible complex. 



2. That the ion-proteids tend to assume the acid or basic properties 

 of the ion, derived from the external solution with which they are com- 

 bined. 



3. The effects of the concentration of electrolytes upon the pro- 

 perties of living tissues are such as to indicate that the reaction between 

 the proteins of the tissue and the ions of the external solution which 

 leads to the formation of ion-2:)roteids is a chemical one, but not so simple 

 as the simple neutralisation of a base by an acid. 



4. The influence of temperature upon living tissues is such as to 

 indicate that the iron-proteid compounds are chemical in nature and not 

 " absorption compounds," but the temperature co-efficient for life- 

 processes is often abnormally high. 



These facts, while leading us, perhaps, to suspect the real chemical 

 nature of the iron proteids, are not in themselves sufficient to enable us 

 to decide as to what chemical types they belong, or to enable us to 

 assert whether or not we can apply the ordinary laws of chemical statics 

 or dynamics to their reactions. In order to answer these questions we 

 must turn to the known chemical properties of the proteins themselves 

 in vitro. 



It has long been known that proteins in solution combine with 

 acids and bases (59). Regarding the compounds with neutral salts there 

 has been more doubt, but the recent researches of Hardy (60), Mellanby 

 (61), and Arny and Pratt (62) appear to place their existence, in some 

 instances at least, beyond a doubt. 



That protean salts are electrolytes — that is, that they ionise in 

 aqueous solution — has been especially pointed out by Mann (63), 

 BUlitzer (64), Freundlich (65), Laqueur (66), and Hardy (67). 



