THE PROBLEM OF MITOGENETIC RAYS 



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of magnitude from that which is thought to be given off by the biological 

 sender. Against these reports stand the pubhcations of Schreiber (251) 

 and others who have not been able to obtain stimulation by artificial 

 light. Since the general field of stimulation as such is still in a very 

 confused state, it may be that a new approach to the problem of stimula- 

 tion will be made possible if the mitogenetic-ray work should prove 

 correct. 



The detector not only responds to certain wave-lengths, but each 

 biological sender is reported to have its own definite spectrum, that is, 

 the radiation given up by each sender has very definite wave-lengths. 

 The sender is placed about 3 to 5 cm. in front of the slit of a medium 

 quartz spectrograph (Fig. 5). The place of the photographic plate is 

 taken either by small yeast-agar blocks, or by a set of tubes of liquid 

 yeast or bacterial suspension. The blocks or tubes are so arranged that 

 each will be exposed to a definite band of the spectrum. It has been 

 reported that it is possible to separate in a medium-size quartz spectro- 



o 



graph bands as small as 10 A units. The materials were exposed for 

 about 2 min., the detectors treated in the standard way, and the percent- 

 age increase determined as usual. A table of typical results (see Table 4) 

 is given. Typical sets of spectra obtained by this method are given in 

 Fig. 6. 



Before going into the biological phenomenon or reaction of the senders 

 themselves, a few words are in place concerning the spectral technique. 

 In spectrographic work certain precautions must be taken, such as the 

 adjusting of the spectrograph, optical adjustments, and others. It 

 is not possible to get uniform results without adjusting the sht carefully; 

 in fact, in order to obtain 10 A bands without overlapping, a fairly narrow 

 slit must be used. It is not obvious that sufficient precautions have 

 been taken to insure a good optical setup with the work reported from 

 laboratories working on this problem. This brings us back again to the 



Table 4. — Spectral Table of Emission from Rabbit's Eye 

 Using yeast instead of photographic plate as detector, with two time intervals and 

 expressing results as percentage effects, plus or minus in comparison with 

 controls (second and third columns) {Gurwitsch, 108; 



