42 NEUTRON EFFECTS ON ANIAIALS 



accumulated dose of 120 n given in only twelve doses. Additional experi- 

 mental data are required before the minimal dose of neutrons and the 

 conditions of irradiation necessary to induce spontaneous tumors can be 

 determined. 



All of the tumors observed from the gross study were found between the 

 skin and muscle layers with no involvement of the latter tissue. From 

 Table II it can be seen that there was a tendency for two tumors to appear 

 together, usually in the axillary region with some in the lateral abdominal 

 wall and inguinal regions. Tumors were identified histologically as pre- 

 dominantly arising from mammary tissue with the formation of chronic 

 mastitis and adenocarcinoma. One rat (X-3, Table II) showed papillary 

 carcinoma of mammary origin, a second (X-10) a reticulum cell sarcoma of 

 lymphoid origin while a third (XI-Bl-5) developed a mixed carcinoma and 

 sarcoma. No tumors were found in the thoracic or abdominal organs 

 although some evidence suggested metastases into some of the internal 

 organs. 



These findings of spontaneous tumor formation during or after neutron 

 irradiation are of prime importance in regard to the safety of radiologists 

 since exposure to low neutron doses over long periods of time may cause 

 serious injury without any prior warning from hematological changes in 

 the peripheral blood. For this reason it seems vitally important that this 

 phase of the neutron problem be investigated further and additional data 

 be obtained on the relationship between repeated exposures to low doses 

 of neutrons and spontaneous tumor formation. 



The present data will not permit of extended comparison of the formation 

 of tumors by neutron rays with those caused by ultraviolet light (Blum, 8), 

 by mesothorium (Gricouroff, 9), and by X-rays (Furth et al., 10, 11). 

 However, it should be noted that Furth cl al. reported the presence of 

 ovarian tumors after X-rays whereas no tumors of this organ were observed 

 after neutron irradiation. Whether or not this indicates a difference 

 between the action of X-rays and neutrons cannot be concluded at this 

 time. 



The data herein reported indicate that neutrons cause efTects comparable 

 to those of X-rays, particularly with respect to changes in the peripheral 

 blood and in the body weight of irradiated animals. In addition, both 

 types of radiation which can produce spontaneous tumors have been used 

 for the treatment of cancer. Recently, CJilman and Philips (12) and also 

 Rhoads (13) have reported that |3-chloroethyl amines produce leukopenia 

 and also have been used in the treatment of cancer. These compounds 

 apparently have an action quite comparable to that of X-rays and neu- 

 trons. It would, therefore, be interesting to see whether these amines 

 would also induce spontaneous tumors if given in extremely low doses over 



