THE PROBLEM OF MITOGENETIC RAYS 929 



It is unfortunate also that no statistical evaluations of the yeast 

 method have been published in which the fundamental data have been 

 critically discussed. Experiments performed with yeast run into many 

 thousands and it is difficult to understand why the evaluation of the 

 probable error of the fundamental procedures has been entirely 

 neglected. 



Many of the foregoing points have been brought out in articles 

 which have come from entirely different laboratories. Attention should 

 be called here to the articles by Schreiber (254), Rossmann (235), and 

 Richards and Taylor (233). None of these authors was able to repeat 

 Gurwitsch's work. In a paper by Rajewsky (226) a statistical evaluation 

 is made and the results given are not the most encouraging. 



Baron (14) believes he has established a so-called "makro-effect." 

 That is, by continuous exposure of a hanging-drop culture of yeast 

 he reports effects which are visible to the eye. As yet no other investiga- 

 tor reports success with this method. Gesenius (84), after exposing 

 yeast suspensions to a mitogenetic-ray sender, tested their fermentation 

 rates with a Warburg apparatus. He reports that he obtained con- 

 sistently a decreased fermentation from the exposed yeast. Gurwitsch 

 (105) explains that the "decrease" effect is caused by too long an exposure 

 to the mitogenetic-ray sender or to an excessive production of secondary 

 radiation. 



BACTERIA AS DETECTORS OF MITOGENETIC RADIATION 



Besides yeast, bacteria have been used extensively as detectors of 

 mitogenetic rays. Early in the development of this field of work the use 

 of bacteria was reported by Magrou and Magrou (177, 181), Sewertzowa 

 (258), and Baron (13), later by Wolff and Ras (306 to 308), Acs (1, 2), 

 and Ferguson and Rahn (71). This method has been developed espe- 

 cially by Wolff and Ras to such a degree that they report what are 

 apparently uniform results. 



Wolff and Ras (309) give the following as worthy of consideration, 

 or conditions to be complied with, if correct results are to be expected: 

 A type of bacteria standardized for the purpose (Staphylococcus aureus 

 is now used almost exclusively by Wolff and Ras); standard bacterial 

 concentrations at the beginning of the experiments (about 400,000 to 

 600,000 per cc.) ; age of culture from which the transfer is made; tempera- 

 ture at which the bacteria are maintained. Bacteria, like yeasts, can 

 be used effectively as detectors only at the time just preceding their 

 maximum growth rate, that is, they should be used during the late 

 "lag" phase. The sample of bacterial suspensions, 2.5 mm.^, is removed 

 to a culture medium; after exposure this is incubated and the number 

 of bacteria determined from the colonies in agar-plate cultures, or, 



