January 21, 1910] 



SCIENCE 



97 



At present only one other organic activator 

 of this kind has been described, namely, 

 the thrombokinase of blood coagulation. 

 This hypothetical substance is given great 

 importance in the theory of coagulation 

 proposed by Morawitz. According to this 

 theory the blood corpuscles under ab- 

 normal environment yield an unknown 

 substance of colloidal nature which to- 

 gether with calcium is necessary for the 

 complete activation of thrombin, and there- 

 fore for the clotting of blood. A similar 

 kinase is furnished by the tissues in gen- 

 eral, so that blood escaping from a vessel 

 and coming in contact with the surround- 

 ing tissues obtains from them a kinase 

 which accelerates the process of clotting. 

 The evidence for the existence of this 

 kinase is far less satisfactory than in the 

 ease of the enterokinase, indeed one may 

 have serious doubts whether the facts at 

 present warrant the assumption that a 

 specific organic kinase must cooperate with 

 the calcium in activating the thrombin, but 

 if the idea is demonstrated to be correct it 

 will furnish another very interesting ex- 

 ample of the way in which chemical coordi- 

 nation may be employed in the body. In 

 this ease the blood may be supposed to 

 stimulate the tissue cells to form a sub- 

 stance not directly of importance to their 

 own activity, but which initiates the coagu- 

 lation of the blood, stops the hemorrhage 

 and thus saves the organism from destruc- 

 tion. The series of events is quite parallel 

 to that described for the pancreatic juice 

 and the enterokinase. 



In addition to the activators of the inor- 

 ganic and the colloidal type there is per- 

 haps a third kind of activation exemplified 

 in the substances known as coenzymes or 

 coferments. This term may be used to 

 define that kind of cooperative activity 

 between an enzyme and some other non- 

 colloidal substance which we see illustrated 



in the influence of the bile salts upon pan- 

 creatic lipase. The process differs from 

 activation of a proferment to a ferment 

 only in that the combination of the enzyme 

 with its activator is dissociable instead of 

 being permanent. By dialysis or otherwise 

 the coenzyme can be separated from the 

 enzyme and the action of the two may be 

 tested separately or in combination. Per- 

 haps this species of activation may be more 

 common in the animal body then 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 CI 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 

 travel in the blood stream to other organs of 

 the body and effect correlation between the 

 activities of the organ of origin and the 

 organs on which they exert their specific 

 effect. Such substances belong to the crys- 

 talloid rather than the colloid class, they 

 therefore are thermostable and do not act 

 as antigens when injected into the living 

 animal. The general idea of this definition 

 is clear and most suggestive, but in its 

 details it is made especially to suit the ease 

 of secretin, and therefore may not fit so 

 well for other substances of like physiolog- 

 ical value. Conveyance through the blood 

 stream, while certainly the most common 

 occurrence for this class of bodies, ought 

 not to constitute an essential part of their 



