1/2 'DESCENT OF MAN ' EXPRESSION. [1872'. 



an eminent degree," namely, " the insatiable longing to dis- 

 cover the causes of the varied and complex phenomena pre- 

 sented by living things." He adds that in the case of the 

 author " the restless curiosity of the child to know the ' what 

 for ? ' the ' why ? ' and the ' how ? ' of everything " seems 

 " never to have abated its force." 



A writer in one of the theological reviews describes the 

 book as " the most powerful and insidious " of all the author's 

 works. 



Professor Alexander Bain criticised the book in a post- 

 script to the ' Senses and the Intellect ; ' to this essay the 

 following letter refers :] 



C. Darwin to A lexander Bain. 



Down, October 9, 1873. 



MY DEAR SIR, I am particularly obliged to you for having 

 sent me your essay. Your criticisms are all written in a 

 quite fair spirit, and indeed no one who knows you or your 

 works would expect anything else. What you say about the 

 vagueness of what I have called the direct action of the 

 nervous system, is perfectly just. I felt it so at the time, and 

 even more of late. I confess that I have never been able 

 fully to grasp your principle of spontaneity,* as well as some 

 other of your points, so as to apply them to special cases. 



* Professor Bain expounded his muscles shall be fresh and vigorous, 



theory of Spontaneity in the essay .... The gesticulations and the 



here alluded to. It would be im- carols of young and active animals 



possible to do justice to it within are mere overflow of nervous 



the limits of a foot-note. The energy ; and although they are very 



following quotations may give some apt to concur with pleasing emotion,, 



notion of it : they have an independent source. 



" By Spontaneity I understand the .... They are not properly move- 

 readiness to pass into movement, ments of expression ; they express 

 in the absence of all stimulation nothing at all except an abundant 

 whatever ; the essential requisite stock of physical power." 

 being that the nerve-centres and 



