THE PROBLEM OF MITOGENETIC RAYS 933 



data. It would be important, particularly, to see confirmatory work 

 from different laboratories. 



PHYSICAL METHODS 



It is often thought that a phenomenon exists only if it is possible 

 to detect it with some purely physical tool. But biologists have often 

 discovered and proved the existence of a new phenomenon long before 

 physical tools were developed for its detection. Many examples from 

 the history of science could be brought forward to demonstrate this 

 point, and it still remains true that even if physical detectors do fail, 

 one may be able to rely on biological methods, that is, if they are handled 

 properly, and if sufficient statistical material is available to evaluate 

 the results beyond doubt. Of course, it is highly important to have a 

 simple physical method of measuring mitogenetic radiation, assuming 

 its demonstration, and for this reason many attempts have been made 

 to develop the necessary apparatus — some allegedly successful. 



Photographing the radiation given up by the sender would suggest 

 itself at once. Most of those who have tried this have not had success. 

 However, some investigators report positive results. The photographic 

 plate is unpromising as a detector of such weak radiation for several 



o 



reasons: the sensitivity of the plate decreases rapidly below X2500 A, 

 and even specially sensitized plates and Schumann plates are at best 

 less sensitive than our fastest plates in the visible. For very small 

 quantities of light the reciprocity law apparently does not hold, that is, 

 it is not possible to irradiate a plate for a very long time with extremely 

 small quantities of light and obtain the same result as would be obtained 

 by giving the total energy at one time. The amount of energy neces- 

 sary to obtain a recognizable impression on the photographic plate 

 is very much higher (about 10~^ erg/cm. ^/sec.) than is supposed to be 

 at the disposal of the investigator working with mitogenetic radiation 

 (10~^ erg/cm. ^/sec). 



Reiter and Gabor (231) report a few experiments with the photo- 

 graphic plate which seem to be successful, but they themselves are not 

 much convinced of their results. A number of other investigators report 

 positive effects with the photographic plate: Brunetti and Maxia (37), 

 Cech (47), Protti (219), Copisarow (55, 56). In all of these cases the 

 work is not explainable on this basis and it may be assumed that these 

 results must have been influenced either by chemical effects or by some 

 other factors which had nothing to do with mitogenetic rays. 



In 1930 Rajewsky (223) published the details of the construction of an 

 apparatus with which he reported he was able to detect as little as 

 10-^2 erg/cm. Vsec. Shortly afterward (224) he reported that he had 

 obtained with this apparatus objective records of the existence of mito- 

 genetic rays. He used a modified Geiger-Miiller counter, an apparatus 



