908 RADIATION BIOLOGY 



Fainstat suggest a degenerative change instead of developmental inter- 

 ference, which seems to occur as a result of other agents. 



Comparison of radiation-induced developmental abnormalities with 

 the changes produced by mutant genes has been made by Russell (1949, 

 1950). Although a particular mutant gene is probably present in every 

 cell of the body, primary gene action is in most cases circumscribed by 

 conditions arising in the course of differentiation. It may be limited to 

 one process, depending on the identity of which the ultimate pheno- 

 typic effect may be either circumscribed or widespread. Or the primary 

 gene action may be widespread, in which case the ultimate expression is 

 even more likely to be a whole syndrome of changes. In any case, it is 

 unlikely that gene action, evoked, as it is, by certain conditions in differ- 

 entiation, should exactly parallel the pattern of radiation effect which is 

 probably determined by some generalized state (e.g., high rate of mitosis) 

 of a variety of precusors. It is, therefore, not surprising that there are 

 no cases of perfect correspondence between all the changes brought about 

 by a given gene and the various abnormalities produced by radiation at a 

 given stage. On the other hand, similarity of certain details may point 

 to the weak links in some of the various developmental chains coexisting 

 at a given moment and should indicate that at least some of the secondary 

 gene effect occurs at the time indicated by the radiation effect. Another 

 possible difference between mutant action and radiation is that, within 

 the affected tissue, the gene may act in every cell, radiation probably only 

 in a certain proportion. This latter property of radiation damage may 

 also differentiate it from the action of physiological poisons, e.g., certain 

 chemicals, and explain its failure to date to produce many of the classical 

 abnormalities — cyclopia, twinning, otocephaly. 



IV. CLINICAL LITERATURE ON THE EFFECTS OF RADIATION 



ON EMBRYO AND FETUS; 



HUMAN IMPLICATIONS OF EXPERIMENTAL WORK 



The case literature on the subject of prenatal radiation effect is large 

 and diffuse but various summaries facilitate a survey of the field, even 

 though they suffer from a certain amount of overlap. In order of 

 appearance, these are by von Klot (1911), Driessen (1924), Murphy 

 (1929), Goldstein and Murphy (1929) (the same material is also found in 

 Murphy, 1947), Gauss (quoting a thesis by Kraemer, 1930), Flaskamp 

 (1930), Schall (1933 — thorough tabular representation), Miller et al. 

 (1936), and Jones and Neill (1944). Cases not included in the above sum- 

 maries are by Lindenfeld (1913) and Murphy et al. (1942). Russell and 

 Russell (1952) have discussed the implications for medical practice of 

 findings in experimental animals. 



Although reports of normal children following prenatal irradiation are 



