ACTION OF X-RAYS UPON PARAMCECIA. 65 



become opaque and deeply blue in color, and the organism had 

 assumed a spherical outline. A few, however, were still slug- 

 gishly active. On the succeeding day, these also died. The 

 control specimens which were treated to the stain in the same 

 manner, but which were unrayed, were still alive on May 26, 

 eight days afterward. On May 22, six other cultures, series F, 

 were rayed 2.5 consecutive minutes after treatment with try- 

 panblau stain prepared as in series A. They had been subjected 

 to this stain for two hours previous to the raying. Very few of 

 these paramcecia were alive on the succeeding day. The majority 

 demonstrated a stained nucleus, spherical outline, and loss of 

 ciliary activity. Controls to this series, however, some of which 

 were rayed unstained for a period of ten minutes, and others 

 stained from 11:15 A.M. to 1:41 P.M., but unrayed, were still 

 alive seven days later, and, judging by their activity, had been 

 unaffected. 



In general this is the result of the action of X-rays upon 

 vitally-stained paramcecia. The quantity of energy necessary to 

 inhibit the activity of unstained paramcecia varies from sixty 

 to eighty milliampere minutes under the conditions of technic 

 given above. When the cultures are stained, as with trypanblau 

 in the concentration mentioned, the amount of energy required 

 to inhibit their activity is reduced to from five to ten milliampere 

 minutes. There is however, considerable variation within certain 

 limits in the susceptibility of the cultures to X-ray energy and 

 also in the rapidity with which they absorb stains. 



So far as could be observed upon these specimens the cause of 

 death was due to an assumption of stain by the nucleus. This 

 causative agent appears to be constant both in the stained but 

 not rayed specimens and also in the stained and rayed specimens. 

 It would appear as if the nuclear membrane were normally 

 impervious to the colloid stain until the degree of concentration 

 of the stain in the cytoplasm became great enough to overcome 

 this resistance. One might assume that X-rays alter this per- 

 meability thus permitting the stains to diffuse readily into the 

 nucleus. 



Solutions of trypanblau, trypan red, neutral red, and of dahlia 

 when exposed to X-ray energy are not fluorescent nor is there 



