EFFECTS OF RAYS OF RADIUM ON PROTOPLASM 343 



gamma rays the results are the same provided the intensity of 

 radiation is equal. The effect is cumulative, and persists 

 through many cell generations (Carrel '14). This is shown also 

 in the experiments on Nereis and on Arbacia. It has also been 

 found that a radiated cancer, in which cell division has been 

 retarded by exposure to the beta rays, may be transplanted 

 several times and still show the effects of the radiation. There 

 is no appearance of abnormal development, or of any visible 

 changes in the cell constituents. The treatment, in every case, 

 has served merely to decrease the rate of normal metabolism 

 without disturbing the process itself. 



A very strong radiation with the beta rays (which must neces- 

 sarily be mixed with the gamma rays) or with all three kinds at 

 once, results in profound morphological changes in the cells. The 

 type of changes thus induced varies in different cells. In the 

 sea urchin and in Ascaris the nucleus is most readily affected. 

 In Nereis, on the other hand, it is the protoplasm which first 

 undergoes degenerative changes. Whether this is due directly 

 to an ionization of the chemical compounds of protoplasm is an 

 open question. Inorganic materials are ionized during radiation, 

 but living matter may not be affected in the same way. A lytic 

 action occurs, as shown in the liquifying of the protoplasm in 

 Nereis, and in the breaking up of the chromatin of Ascaris and 

 other forms. 



These profound changes in the physical constitution of the 

 cells is accompanied by changes in the behavior of their con- 

 stituents. In this respect cells differ greatly. In Ascaris the 

 achromatic portion of the mitotic figure is uninjured, while the 

 chromatin is broken up into granules. In Nereis, on the con- 

 trary, the chromosomes split with great precision, but the spindles 

 are abnormal and are sometimes entirely absent. But I have 

 never found an egg so injured that it did not make some attempt, 

 however abortive, to go through its usual development. 



The hypotheses which have been advanced in explanation of 

 the phenomena which follow a severe radiation were discussed 

 in a previous paper (Packard '14). Hertwig's view, which is 

 based on a study of forms in which only the chromatin is injured. 



