Cancer. 413 



durative. The epithelial elements in such examples may become 

 very unimportant structural factors; these hard specimens arc 

 known by the names scirrhus. scirrlious cancer. 



According to statistics compiled by Casper, Frohner and Sticker, 

 cancers [among animals] are most frequent among dogs (three 

 per cent.) ; horses rank next in order, and after them cats. 

 Just as in man cancer in animals is a disease developing principally 

 in middle and later life. This is probably the reason for the in- 

 frequence of these tumors in cattle, sheep, goats and swine, such 

 animals not attaining an advanced age because of their use for meat 

 supplv. The skin and its junctions wdth the mucous membranes 

 are the most frequent seat of growth [for squamous epitheliomata] , 

 anal cancer in the dog and cancer of the glans penis, gums 

 and lips in the horse being frequently met with. The mammary 

 glands and thyroid gland of the dog are comparatively frequent 

 points of primary involvement [adenocarcinoma or carcinoma sim- 

 plex according to the degree of atypical structure to which the 

 growth is advanced]. 



In human beings cancer of the stomach and of the female uro- 

 genital organs constitute a high proportion of these growths; in 

 animals these organs are afifected by cancer to a far less degree.* 

 As far as the rest of the body is concerned it may be said that pri- 

 marv cancer has been observed in all the epithelial organs. In 

 structures which do not possess epithelial cells (lymphglands, mar- 

 row, spleen, muscles, etc.) cancer can occur only in metastases (in 

 rare exceptions also from embryonal germinal misplacements). 

 Such metastatic growths sometimes become of greater bulk than 

 the primary tumor, especially those of lymph glands. f 



The general peculiarities of cancerous growths, their irrepressi- 

 ble penetration into the tissues in every direction, the difficulty of 

 thorough operative removal of all their roots which is only occa- 

 sionally successful in the early stages of the cancer and if incom- 

 ' pletely accomplished invariably results in recurrence, the destruc- 

 tion of the affected organ and the certainty of metastasis, stamp these 

 tumors as highly malignant autoblastomata. In the course of the 

 cancerous affection, the severity of which is determined by the rap- 

 iditv of dissemination and the location of the growth and the impor- 

 tance of the tissue involved, there usually develops a condition of 



* For details see esp-cially the statistics of Sticker, ArcJiiv. f. Kliiiisch. Chir- 

 itrgie, Bd. 6.5, Berlin, 1901'. 



t If the primarv growth has been removed by operation and this fact be 

 nnknown to the examiner, or if the scar at the affected place be oyorlookech the 

 secondary formations mav give the erroneous impression of being primary tumors. 



