246 E VOL UTION A ND DISEASE. 



founded, nor is the distinction always made with the 

 accuracy that is essential in order to enable us to draw 

 conclusions from statistical tables as to the frequency of 

 cancer in comparison with other tumours. 



Another circumstance which has never received full 

 attention is the great frequency of cancer in the white 

 races of mankind. A careful and extensive inquiry into 

 this question is very desirable, for we are grossly igno- 

 rant as to the occurrence of cancer among the natives of 

 colonies, even of India. 



Again, cancer, using the term in the sense in which 

 it is employed throughout this chapter, is rare among 

 domesticated mammals, and rarer still among wild 

 mammals, even those living in captivity. To take one 

 example, cancer of the uterus, which is responsible for 

 the death of an appalling number of women every year 

 in England, is, as far as my inquiries have extended 

 among veterinarians, as well as from my own observations, 

 very rare in domesticated and wild mammals. 



The cause of the extreme frequency of cancer in one 

 case, and its absence in another, may be in a measure 

 explained by certain peculiarities in structure and gland 

 distribution. The question is far too extensive to be 

 adequately considered in such a work as this, and 

 when I have pushed my investigations further I hope to 

 deal with it in a systematic manner. 



Before leaving this subject it will be interesting to 

 describe a specimen illustrating the close relation which 

 exists between glands and cancer. In the section de- 

 voted to supernumerary mammae, I drew attention to the 

 relation existing between cutaneous recesses and glan- 



