CANCER BE SEARCH 29 



character of the work and the development of cancer. For instance in 

 Eontgen ray technicians, especially in those who began their work, in 

 the first years following the discovery of the rays, when the dangers con- 

 nected with this occupation, the various precautions used at the present 

 time were as yet unknown, gradually, often after many years of work, a 

 painful condition of the skin arose, mainly on the hands and arms which 

 were exposed to the rays, it became thickened, cracked, ulcers formed. 

 The epithelium grew further down into the deeper tissues and slowly 

 a carcinoma developed which later made metastases. 3 Approximately 

 70 cases are known where cancer thus developed, and in some cases it 

 developed a considerable time after the exposure to the Eoentgen rays 

 had ceased. 



Chimney sweeps develop relatively frequently cancer of the skin, 

 especially of the scrotum, and it is interesting that this cancer may be 

 found in young people. It has for instance been observed in a boy eight 

 years old. The cause of this cancer is the irritation produced by soot. 

 Those who are employed in the distillation of tar (especially of gas work 

 tar) in the manufacturing of grease and briquettes are liable to develop 

 cancer of the skin. Certain organic substances contained in tar and 

 pitch cause the development of warts on the skin, which later break 

 down and become transformed into cancers. In men employed in the 

 manufacturing of aniline dyes, and certain other benzol derivatives, 

 wartlike excrescences of the skin may appear ; but especially interesting 

 is the frequent appearance of cancers of the bladder in such cases. Each 

 of the affected men had been in the dye works for 20 years or more. 

 Evidently substances excreted through the kidneys exert in such cases 

 an irritating action on the epithelium of the bladder. 



There are some other occupations in which certain substances are 

 the direct or indirect cause of the development of cancer. Just as 

 Eontgen rays and certain chemicals, so may also light rays under certain 

 conditions be the cause of cancer, especially in sailors, in whom some- 

 times the skin of that part of the body which is exposed to the light 

 shows certain changes which lead gradually to the development of 

 cancer. "We notice also occasionally in old people and in rare cases even 

 in young men in the face and on the hands, in parts therefore exposed 

 to the action of the light rays, the development of multiple lesions, 

 which in the course of time become transformed into carcinoma. There 

 occurs furthermore in children a congenital skin disease, xeroderma pig- 

 mentosum, which develops usually into a carcinoma at places exposed to 

 the light rays. 



Very instructive is the cancer which is not rarely found in Kashmir 

 among the carriers of the kangri, a little stove, which burns the skin on 

 which it rests. Gradually cancers develop in the scars ; the downgrowth 

 s Cf., the careful microscopical studies of S. B. Wolbach. 



