THE PROBLEM OF MITOGENETIC RAYS 921 



is the further complication of the very low intensity of the reported 

 mitogenetic rays — a factor which increases materially the difficulties 

 of the problem. To these two factors we must add the third and most 

 important one — that of the proper handling of the material which gives 

 off the radiation. 



Because of the low intensity of the radiation, it is almost outside 

 the range of our most sensitive physical instruments. As a matter of 

 fact, a special instrument has been designed, and with this, in the hands 

 of some investigators, the detection of the rays has been reported. 

 Those who have used this physical detector, a modified Geiger-Miiller 

 counter, have announced the detection of the rays from relatively 

 few senders. Thus, it seems that with any investigation in this field 

 one must count, in the main, on a biological detection. That biological 

 detectors may be more sensitive than the most sensitive physical instru- 

 ments will not surprise the biologist, who reaHzes that many biological 

 materials are influenced by factors which are as yet imperceptible with 

 our most sensitive physical and chemical tools. 



The high sensitivity of the biological indicator makes it a dangerous 

 material with which to work. Merely to keep biological materials 

 in a perfectly uniform condition presents difficulties, but to keep the 

 materials so that they may take the place of and improve upon physical 

 instruments is a problem in itself. Such work requires the utmost 

 experience with the material, carefully devised precautions in the pro- 

 cedure, and a painstaking evaluation of replicated results. In reading 

 numerous reports in this field of work it has not always been apparent 

 that these precautions have been taken; and sometimes only meager 

 evidence has been used; in fact, not infrequently there is evidence that 

 the precautions are inadequate and the data meager, yet these have 

 supported extensive speculations. 



EARLY WORK OF GURWITSCH AND OTHERS 



It is a well-known fact that many living organisms give up visible 

 light. This has been adequately investigated and good reviews on 

 the subject are available (Harvey, 141, Mangold, 186). It does not 

 seem improbable that ultra-violet radiation should be given up by 

 living materials, although it is somewhat less probable from the physical 

 point of view (Daniels, 61). It was this probability which led Gurwitsch 

 in 1922 (92) to come by way of theoretical considerations to the conclu- 

 sion that there are, besides obvious chemical effects, certain physical 

 phenomena which have a deciding influence upon cell division, the source 

 of which must lie within the living material. Gurwitsch's (93) search 

 for this source of influence brought him to the study of the influence 

 of certain biological materials in various stages of their development; 

 and for these first experiments he used onion roots. The method of 



