September 3, 1915] 



SCIENCE 



297 



can be used to influence the activity of the 

 cell extractive called fertilizin. This sub- 

 stance is extracted from sea-urchin and star- 

 fish eggs when the ripe eggs are allowed to 

 stand in water for a short time, and it pos- 

 sesses the property of causing the agglu- 

 tination of the sperm of its own species. 

 Its behavior is in some respects comparable 

 to that of an enzyme and it is possible 

 that the substance contains enzjonotic 

 bodies. The experiments showed that radia- 

 tion by X-rays is capable of changing the 

 activity of fertilizin, and in general agrees 

 with previous work that weak radiation is 

 accelerative and strong inhibitive. Fertilizin 

 is a substance derived from the living eggs 

 and the extraction takes place while the 

 egg is in the resting stage, sometimes even 

 in the germinal vesicle stage; at this stage 

 chromatin can scarcely play any part in 

 the giving off of fertilizin. In this case, 

 then, the radiation has had a considerable, 

 and a measurable, effect on a cell substance 

 independent of the chromatin or other nu- 

 clear structures. This fact can hardly be 

 brought in line with the Hertwig hypoth- 

 esis in its present form. 



Yet it is true that chromatin and nu- 

 clear structures are greatly changed by 

 radiation. In any true explanation that 

 may be given this important fact must be 

 dealt with. It is possible that a modifi- 

 cation of the present form of the Hertwig 

 theory in which the effect on enzjrmes is 

 recognized may be sufficient to account for 

 all the facts that are now known. 



Packard has attempted such a modifica- 

 tion in his suggestion "that the radium 

 radiations act indirectly on the chromatin 

 and protoplasm by activating autolytic 

 enzjrmes which bring about a degeneration 

 of the complex proteids, and probably by 

 affecting other protoplasmic substances in 

 the same manner." Against this hypoth- 

 esis there is little that can be urged except 



the fact that it rests upon insecure evi- 

 dence, there being but few actual observa- 

 tions or experiments which contribute to it. 

 It is certain that radiation influences the 

 activity of various en^iymes, but there is 

 very little evidence upon which to base the 

 assumption necessary to the hypothesis that 

 those enzymes which cause katabolic 

 changes in the cell proteids are accelerated 

 to a greater extent than those which have 

 the opposite function. For this reason 

 judgment can only be suspended until such 

 a time shall come when accurate and more 

 abundant data are at hand for attacking the 

 problem. 



Joly'-^ has proposed a different kind of 

 explanation to account for x-ray effects. 

 Comparing the events which take place in a 

 photographic film with those which occur in 

 cells subjected to gamma or to rr-rays, he 

 supposes that the rays increase ionization in 

 the tissue. The various results found are 

 accounted for as due to differing degrees of 

 ionization and to the presence or absence of 

 an "intensifier" or an "inhibitor." No 

 evidence from biological studies is given to 

 support this hypothesis, however; it must, 

 therefore, await experimental confirmation. 



It will be seen from the foregoing review 

 that all the investigations which have con- 

 tributed to the development of these vari- 

 ous theories either have had a morpholog- 

 ical basis or were of a chemical nature. 

 Along these lines there remains a great deal 

 to be accomplished ; we especially need more 

 exact information on the nature of the in- 

 jury which is done to the chromatin and to 

 the cell organs. 



But in addition to the morphological 

 study the general problem must be studied 

 by other methods. The question is raised 

 as to what is the nature of the stimulus by 



1' Joly, J., "A Theory of the Action of Eays on 

 Growing Cells, ' ' Proc. Boy. Soc, Series B, Vol. 88, 

 1914. 



