detailed examination. This examination re- 

 vealed that when the strongest of the doses used 

 by these authors was applied, the cells that were 

 already in mitosis before irradiation (even if 

 they were in very early prophase) would com- 

 plete their division. These observations indi- 

 cate, therefore, that the decrease in number of 

 cells which undergo mitosis and the absence of 

 cells in mitosis is due, not to the injury, death, 

 or decomposition of the cells undergoing mitosis, 

 but to the inhibition of development of those cells 

 which had not yet entered or had just begun mi- 

 tosis at the time of irradiation. This explains 

 the apparent contradiction between the conditions 

 of the cultures observed immediately after irra- 

 diation and those observed 80 minutes later. 



Bersa (1927) traced the action of X rays on 

 cellular elements with particular care. By 

 means of a comprehensive series of experiments 

 he established that the greatest number of path- 

 ological mitoses can be observed after 36 and 48 

 hours. A careful examination of these mitoses 

 leaves the impression that the chromatin has 

 undergone substantial changes: the chromosomes 

 tend to contract, to stick together, to fragment. 

 These signs indicate that the viscosity of the 

 protoplasm has diminished and that the surface 

 tension has increased. From this there is a 

 tendency towards the stretching of the threads 

 (the formation of bridges), on the one hand, and 

 the rounding out into drops, on the other. 



Pekarek (1927) approached this question very 

 thoroughly in his article. He concentrated on 

 studying the effects of X rays on mitoses, their 

 frequency, and on chromosome changes. How- 

 ever, like Bersa, he thinks that the primary 

 effects of X rays should be sought in changes in 

 the colloidal condition of the protoplasm. 



Nadson and Rokhlina [-Gleikhgerikht] have 

 done important work in this area (1926, 1933 

 [and 1934]). They examined the cells of the 

 irradiated epidermis of onion scales in a living 

 condition immediately after irradiation, after a 

 half hour, after an hour, and so on up to 48 

 hours. The first consequence of irradiation that 

 the authors were able to trace was an increase 

 in the rate of protoplasmic movement. How- 

 ever, a depression soon sets in, as manifested 

 in a slowing down of the movement of fat glob- 

 ules and chondriosomes, and in a weakening of 

 the Brownian movement. This, in turn, indi- 

 cates an increase in viscosity of the protoplasm. 

 Finally, the movement of the protoplasm stops 

 altogether; an hour later the strands of proto- 

 plasm disappear and the protoplasm collects in 

 the corners of the cell. At the same time the 

 protoplasm, originally fluid and homogeneous, 

 becomes turbid. This indicates a weakening of 

 its dispersion. At this time, the nucleus also 

 begins to change — its granular structure be- 

 coming more coarse, the outlines of the nuc- 

 leus and the nucleolus more distinct. Then fat 

 droplets appear in the protoplasm, pointing to 



the breakdown of the lipoproteins due to the 

 X rays; this phenomenon is lipophanerosis. At 

 approximately the same time (i. e. , 2 to 3 hours 

 after irradiation), vacuoles appear. Twenty- 

 four hours after irradiation the protoplasm 

 becomes pale, completely transparent, and 

 watery. 



At the same time the vacuolization becomes 

 more intense, the structure of the protoplasm 

 becomes coarsely foamy, and lipophanerosis 

 continues. Finally, the structure of the proto- 

 plasm becomes bubbly, and on the surface of 

 the bubbles numerous fat globules appear. 

 Except for the lipophanerosis the same changes 

 can be observed in the nucleus as in the proto- 

 plasm, i. e. , coagulation, vacuolization, and 

 karyolysis (the dissolution of the nuclear mate- 

 rial). The nucleolus disappears. During 

 degeneration the outline of the nucleus very 

 frequently becomes irregular and highly varia- 

 ble. The rate of change depends primarily on 

 the length of irradiation, but also on the physio- 

 logical condition of the cell. 



Nadson (1935) devotes a separate chapter to 

 X-ray-induced changes in protoplasm. It is 

 extremely interesting that he associates these 

 changes with the Arndt-Schultze Law (see Chap- 

 ter 1 of this book) according to which small 

 doses stimulate cellular activity, stronger doses 

 depress it, and still stronger doses kill the cell. 

 Nadson considers that he not only succeeded in 

 confirming this law, but also discovered the 

 principles underlying its action, since cells 

 affected by irradiation pass through definite 

 phases, each of which has its distinctive mor- 

 phological and physiological features. The first 

 phase is characterized by the fact that the cellu- 

 lar protoplasm becomes agitated, as can be 

 seen from the quick and varied changes in the 

 vacuoles. The protoplasm becomes swollen with 

 water and its dispersion and penetrability in- 

 crease. This is the phase of stimulation. This 

 process is reversible. The second phase is the 

 dispersive phase when the life processes are 

 slowed down. The protoplasm, originally trans- 

 parent and homogeneous in appearance, becomes 

 somewhat turbid, then finely and delicately dis- 

 persed, which indicates a lowering of dispersion. 

 The protoplasm loses water, becomes less 

 swollen, and its penetrability diminishes. The 

 vacuoles become considerably larger. Almost 

 at the same time the disintegration of the lipo- 

 protein complex (lipophanerosis) takes place. 

 These phenomena are still reversible if they 

 have not gone too far. The third phase is a 

 phase of even more profound, and clearly path- 

 ological changes, of disorganization and more 

 or less quick process of dying off — of necro- 

 biosis and, finally, death. This phase is char- 

 acterized by the onset of coagulation of the 

 protoplasm, the continuation of the processes of 

 losing water, and the final dissolution of the 

 lipoprotein complex. The permeability of the 

 protoplasm increases sharply, plasmolysis takes 



60 



