FISHES 165 



seem to have nothing to do with each other may 

 influence each other. Thus, when a man is emasculated, 

 he retains the high voice of the boy, and never grows a 

 beard. Women who are about to become mothers 

 suffer from nausea, vomiting, and a number of other 

 afflictions. In a word, we have numerous proofs of the 

 co-operation of different parts of the body. 



Thus, when an organ has been adapted to new 

 conditions and modified in the making of a new 

 species, a structure may arise in another part of the 

 body from a chain of causes that escapes our scrutiny. 

 We put chandeliers in our rooms to light them, for 

 instance. But we heat them at the same time, as well 

 as illuminate them. This is a constant and necessary 

 concomitant of the lighting. We had no intention of 

 causing it, but we have to reckon with it because we 

 cannot have the gas-light without it.^ 



Owing to correlation many organs may be preserved 

 that are of no consequence to the animal's life. Other 

 and important organs prevent them from changing their 

 dimensions or quality, because they are in some way or 

 other connected with them, and as they themselves must 

 remain in the interest of the species, they retain the 

 others with them. However, we will make as little use 

 as possible of this principle of correlation, because we 

 know little about the mutual relations in the animal 

 body, and so the whole principle is not well grounded 



^ Many writers explain in this way the colours of the various races 

 of men. They think it is a necessary concomitant of the adaptation 

 of the skin to different degrees of heat ; the skin does, in point of fact, 

 behave differently in relation to perspiration and immunity against 

 fever. 



