9 



Radiation Cytology 



The fact that ionizing radiation of the X-ray type has a marked effect 

 on genetic material was established in the late twenties primarily through 

 the work of H. J. Muller (1928), Altenberg (1928), and Stadler 

 (1928). These workers all showed quite conclusively that there is a 

 marked correlation between exposure to X rays and increase in produc- 

 tion of mutant offspring. Their results were quickly confirmed and ex- 

 tended by both genetical and cytological studies. The latter soon pro- 

 vided data indicating that degree of chromosome damage was also quite 

 directly correlated with dosage (Sax, 1938, 1940). Since the dawning 

 of the so-called Atomic Age in 1945, interest in the biological con- 

 sequences of exposure to ionizing radiations of all sorts has been greatly 

 intensified. Despite all these efforts there are still many blanks in our 

 knowledge, especially concerning the manner in which radiation pro- 

 duces its effects. In this chapter we will outline the salient facts, con- 

 cepts, and problems with which radiation biology is currently concerned. 



EFFECTIVE RADIATIONS 



Ionizing radiations are those which, upon being absorbed, directly or 

 indirectly produce ion clusters. These include X rays, gamma rays, alpha 

 particles, beta rays, neutrons, and protons. Despite considerable differ- 

 ences in primary action, all of these waves and particles ultimately in- 

 duce more or less dense clusters of ion pairs. The consequent local 

 instability is presumably reflected in disruption of many molecules. Non- 

 ionizing radiation, especially short waves in the ultraviolet range, pro- 



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