l66 THE EVOLUTION OF MAN. 



thougli Physiology had in the pursuit of its own objects 

 occasion enough to devote itself earnestly to the study of 

 these functions. In the same way the important functions 

 of growth and coalescence, as also those of differentiation 

 and atavism, have as yet been very little studied from a 

 physiological point of view. 



This neglect of the history of evolution explains the 

 little interest and the lack of insight exhibited by the 

 physiologists of our time with regard to the theory of 

 descent. When Darwin, in his Theory of Natural Selection, 

 gave a new basis to the theory of evolution, and so pointed 

 out the way to a physiological explanation of the formation 

 of species, a new and most interesting field of research was 

 thrown open to Physiology. But Physiology has hardly yet 

 entered this; and it has done as little to advance our 

 knowledge of the processes of evolution in their ontogenetic 

 as in their phylogenetic aspect. In fact, with a few 

 illustrious exceptions, most physiologists have paid very 

 little attention to the theory of descent, and to this day 

 some of their most renowned leaders look on this most 

 important biological theory as "an unproved and baseless 

 hypothesis." 



This want of comprehension of the history and signifi- 

 cance of evolution can alone explain, for instance, the fact 

 that the famous Berlin physiologist, Du Bois-Reymond, in 

 his well-known address " On the limits of Natural Science," 

 delivered at Leipsic in 1872, before the meeting of German 

 naturalists, declared human consciousness to be a phenome- 

 non absolutely and unconditionally transcending the bounds 

 of human comprehension. It never occurred to him that 

 consciousness, in common with every other cerebral activity. 



