188 MODERN SCIENCE READER 



that a specific organic kinase must cooperate with the cal- 

 cium in activating the thrombin, but if the idea is demon- 

 strated to be correct it will furnish another very interesting 

 example of the way in which chemical coordination may be 

 employed in the body. In this case the blood may be sup- 

 posed to stimulate the tissue cells to form a substance not 

 directly of importance to their own activity, but which ini- 

 tiates the coagulation of the blood, stops the hemorrhage 

 and thus saves the organism from destruction. The series 

 of events is quite parallel to that described for the pan- 

 creatic juice and the enterokinase. 



In addition to the activators of the inorganic and the 

 colloidal type there is perhaps a third kind of activation 

 exemplified in the substances known as co-enzymes or 

 co-ferments. This term may be used to define that kind of 

 cooperative activity between an enzyme and some other 

 noncolloidal substance which we see illustrated in the 

 influence of the bile salts upon pancreatic lipase. The 

 process differs from activation of a preferment to a fer- 

 ment only in that the combination of the enzyme with its 

 activator is dissociable instead of being permanent. By 

 dialysis or otherwise the co-enzyme can be separated from 

 the enzyme and the action of the two may be tested sepa- 

 rately or in combination. Perhaps this species of activa- 

 tion may be more common in the animal body than we have 

 supposed. Bierry and Giaja have shown that the amylase 

 of pancreatic juice loses its diastatic action entirely when 

 dialyzed, and this power or property is restored upon the 

 addition of sodium chloride. It would seem from their 

 experiments that the amylase is active only when combined 

 with an acid ion, such as Cl or Br, and the transition from 

 one form to the other, from the active to the inactive or 

 the reverse, is easily accomplished. No one can doubt that 

 all these forms of chemical activation are allied in a general 

 way to the more interesting and obvious mode of chemical 

 coordination illustrated by the hormones. Starling defines 

 hormones as chemical messengers which formed in one organ 



