MORPHOLOGIC AND PATHOPHYSIOLOGIC SIGNS 307 



nomena in frogs after prolonged exposure of an isolated nerve to beta rays. 

 Vasilev (1957) observed the development of parabiosis in a nerve conductor 

 after its exposure to alpha radiation. Bakin, Dolgachev, and Lomonos 

 (1952) pointed out that not all the constituent parts of a peripheral nerve 

 possess equal radiosensitivity. The excitability of the sensory parts is first 

 observed to increase; later, sensitivity diminishes, and only after this has 

 occurred do we find disturbance of the motor functions. 



Disturbances of the receptors and the consequent prolonged pathologic 

 transmission of impulses from the periphery can play no small part in the 

 nervous system's response to irradiation. 



Geinisman and Zhirmunskaya (1958) observed intensified transmission 

 of impulses from the carotid sinus zone and the skin of a frog after these 

 structures had been exposed to radiation. 



Tsypin (1956) noted a sharp intensification of the impulses reaching the 

 nervous system from the eyes immediately after exposure to radiation. 



Zaretskaya (1956) noted phase variations in the impulses arriving from 

 the chemoreceptors of the lymphatic ganglia of cats after exposure to 

 radiation. 



Delitsina (1957) showed that after a rabbit's extremities had been exposed 

 to 500 r there was at first a sharp intensification of impulses from the irradi- 

 ated part, followed by subsequent weakening. 



Chernichenko (1957), by exposing the urinary bladder and one of the 

 intestinal ansae to local irradiation, established that this caused a disturbance 

 in the character of impulses arriving from the receptors of the aflfected 

 organ. 



The fact that tolerance of radiation damage varies greatly from one sub- 

 ject to another has led several research workers to pay attention to individual 

 characteristics. It has been found that resistance to the effect of radiation 

 depends largely on the type of higher nervous activity. Animals with well 

 balanced higher nervous activity withstand ionizing radiation best; disturb- 

 ances of the nervous activity due to the effect of radiation develop later in 

 these animals, even after exposure to large doses. 



Lomonos (1959) notes that in dogs with a strong type of higher nervous 

 activity, the conditioned reflex activity and the capacity to differentiate are 

 maintained even on exp>osure to lethal doses of radiation. 



Khruleva (1958) showed that a temporary lowering, followed by a pro- 

 longed heightening of the conditioned reflex activity, occurred in dogs with 

 poorly balanced higher nei'vous activity when the animals were exposed to 

 comparatively small doses of gamma radiation (50 r). In animals with a 

 weak type of nervous system, such irradiation caused serious disturbances of 

 the conditioned reflex activity, passing into prolonged neurosis. 



Similar results were obtained by Klimova (1957), Kurtsin (1957), 



