58 THE CELL 



catarrhal symptoms of the conjunctiva palpebralis, inflammation and swelling 

 of the conjunctiva oculi, desquamation of the epithelium and clouding of the 

 cornea, as well as contraction of the pupil and discoloration of the iris. Similar 

 effects appear on the skin : it becomes red and swollen ; burning sensations 

 and sensitiveness to touch distinguish the affected portions; after some days 

 the epidermis begins to peel off in the form of large scales, and in about 

 fourteen days the skin becomes normal again. There usually remains for 

 a long time, however, a light coloration of the affected part, which is sharply 

 marked off from the surrounding skin (Widmark). With sufficient concen- 

 tration of the light, the blue-violet rays also are said to exercise a similar 

 influence (Finsen). 



The X rays discovered by Rontgen produce in the skin similar but even 

 more powerful effects than those discussed above. Possibly the ultra-violet 

 rays contained in the cathode rays contribute in some degree to this effect. 

 Certain Bacteria (the cholera, anthrax, diphtheria, and tubercle bacilli) are 

 killed by the X rays, and cells of higher plants suffer a reduction of their 

 activities. Different Protozoa exhibit a very different power of resistance 

 toward the X rays (of fourteen hours' duration) : some forms appear not to be 

 affected by them at all, others slightly, some very powerfully. In general it 

 appears that forms which have vacuolated protoplasma react more quickly 

 than those of firmer structure. The presence or absence of membranes and 

 shells may also be significant (Schaudinn). 



With respect to the Becquerel rays (radium) Aschkinass and Caspari 

 have found that they weaken markedly the Bacillus prodigiosus in from two 

 to four hours. With a longer exposure to radium (twenty-four and sixteen 

 hours respectively) typhoid and cholera bacilli were killed (Pfeiffer and 

 Friedberger). Schwarz has shown further from researches on the hen's egg 

 that these rays destroy albuminoid bodies by a kind of dry distillation, that 

 they decolorize lutein and act upon the lecithin of the cell substance. In these 

 effects he finds the explanation of the peculiar cell necrobiosis observed by 

 Becquerel himself. Becquerel once carried in his vest pocket for only two 

 hours a well-wrapped but highly active radium preparation. Fourteen days 

 later he observed on the abdominal skin opposite the pocket a small burn 

 which became larger and larger and finally developed into a deep wound 

 which did not heal for months. 



F. STIMULATION BY MEANS OF HEAT 



Only in relatively few cases does heat appear to exercise a direct stimu- 

 lating effect on living cells. In the higher animals only the end organs of 

 certain afferent nerve fibers are really roused to activity by heat. Heat, as 

 already remarked above, exercises a more powerful influence on the excita- 

 bility of the cells. In all cells we find that the life processes increase in 

 intensity with the temperature up to certain limits (cf. supra page 29), and 

 likewise that with a lowering of the temperature they are depressed at least, 

 if not brought to a complete standstill. It is not easy in any given case to 

 separate clearly the actually stimulating effect from the heightening influence 



