ORGAN AND BODY SYSTEMS 475 



so-called sensitivity of the organs (376). The manner in which the 

 dosage may be varied by organs of different density, the presence of gas 

 and air in certain organs, and other factors was discussed by Wintz and 

 Rump (392). Tsuzuki (354) irradiated normal rabbits with 160 per cent 

 of human skin erythema dose (with average wave-length of 0.1 A, 

 170 kv.) and studied the depth dose developed in various organs. This 

 is a very rational attempt to arrive at the sensitivity of the various organs. 

 Weatherwax and Robb (382) showed considerable difference in the depth 

 dose when collapsed and expanded lung tissue was immersed in a water 

 phantom. The expanded lung allows more radiation to pass through the 

 w^ater, although there is a reduction in the amount of scattered radiation. 

 A critical inspection of published data would indicate that up to the 

 present time there are no accurate dosage tables for the total destructive 

 dosage, or ''lethal" dosage, for any of the cell types in vivo. Little 

 consideration (except Tsuzuki, 354) has been given to the effective depth 

 dose deUvered to an organ in situ (Packard, 260), especially in experi- 

 mental animals, and it is apparent that most of the effects obtained in 

 organs following irradiation are in various degrees of totality. Most 

 investigators have manipulated dosage to the point of obtaining an 

 appreciable, destructive, structural change, either microscopic or gross, 

 with some demonstrable functional abnormality. There are several 

 important handicaps to experiment: (a) the technical difficulties in 

 handling the experimental animal or biological material and the cumber- 

 some physical equipment in an accurate manner during the period neces- 

 sary for the irradiation; (b) the difficulty in localizing the radiation and 

 measuring the amount delivered to the organ; (c) the variation in the 

 biological materials, in regard to both individual and species differences ; 

 (d) the difficulty in interpreting results w^here the normal variables are 

 not well understood either in the laboratory animal or in the greatest 

 variable, the diseased patient. 



GENERAL CONCEPT 



Fundamentally, there are two major types of change that radiation 

 may bring about in a cell, and thus in an organ, namely, an acute fatal 

 injury or an injury which is not necessarily fatal but which leads to 

 degenerative changes of greater or less degree, such as edema and swell- 

 ing, faulty mitosis, shrinkage in size, and in extreme cases, loss of nuclei 

 and hyahnization. An infiltration of wandering cells may occur, but 

 this is often negligible in quantity and is probably a repair reaction. 

 With destruction of sensitive cells, the connective-tissue stroma which is 

 sometimes also damaged, tends to collapse and become more prominent, 

 and the repair reaction tends to bring in new connective tissue cells to 

 fill up the spaces left by the disappearance of the cells of an organ. This 

 does not take into consideration, of course, those cells only slightly 



