172 C. M. CHILD. 



velopment of bone and connective tissue and many other similar 

 cases micfht be mentioned. It is conceivable that in some form- 



o 



ative processes the most important conditions are chemical rela- 

 tions, but even in such cases the chemical constitution of a given 

 substance is only indirectly "formative." 



Moreover, in many other dynamic phenomena occurring both 

 within and outside of the organism the chemical composition is 

 of little importance. The catalytic activity of colloid solutions 

 of metals does not appear to differ fundamentally from that of 

 enzymes and yet the substances involved are widely different ; in 

 many of the effects produced by electrolytes one chemical ele- 

 ment or radical may be substituted for another without altering 

 the result : compounds of widely different chemical composition 

 may produce identical osmotic phenomena, etc. In short, chem- 

 ical constitution is at best only one of a large number of factors 

 involved and often is of little or no importance. 



Morphogenetic properties have been assigned by various 

 authors to specific enzymes and to other substances of more or 

 less definite chemical constitution. For example, in a recent paper l 

 L. Loeb makes the following statement : " Ferments produce pri- 

 marily chemical changes. But we know of chemical ferment 

 actions which bring about structural changes in the medium in 

 which they act. Thrombin in transforming fibrinogen into fibrin 

 changes a colloidal fluid into a gelatinous, more or less solid 

 mass, which under the influence of pressure and traction may 

 show a fibrillar structure not unlike connective tissue. From a 

 certain point of view the fibrin ferment may therefore be regarded 

 as a form-producing ferment. We might call it a morphogenetic 

 ferment. We have reason to assume that there exist other mor- 

 phogenetic ferments" (p. 150). 



A critical examination of this statement will at once render it 

 evident that the real formative factors in the production of the 

 fibrillar structure are the pressure and traction, and not the 

 enzyme. The enzyme simply changes the condition of the 

 medium in which it acts in such manner that pressure and 

 traction produce a visible structural effect. But the enzyme 

 itself is not properly speaking morphogenetic. The other cases 



1 Immunity and Adaptation. BlOL. BULL., Vol. IX., No. ?, 1905. 



