PROFESSOR VIRCHOW AND EVOLUTION 397 



contrast with this the notion entertained by the philos- 

 opher Ueberweg, one of the subtlest heads that Germany 

 has produced. "What occurs in the brain," says Geber- 

 weg, "would, in my opinion, not be possible, if the proc- 

 ess which here appears in its greatest concentration did 

 not obtain generally, only in a vastly diminished degree. 

 Take a pair of mice and a cask of flour. By copious 

 nourishment the animals increase and multiply, and in the 

 same proportion sensations and feelings augment. The 

 quantity of these latter possessed by the first pair is not 

 simply diffused among their descendants, for in that case 

 the last must feel more feebly than the first. The sensa- 

 tions and feelings must necessarily be referred back to 

 the flour, where they exist, weak and pale it is true, and 

 not concentrated as they are in the brain. ' ' ' We may 

 not be able to taste or smell alcohol in a tub of fermented 

 cherries, but by distillation we obtain from them concen- 

 trated Kirschwasser. Hence Ueberweg's comparison of 

 the brain to a still, which concentrates the sensation and 

 feeling, pre-existing, but diluted in the food. 



"Definitions," says Mr. Holyoake, 9 "grow as the hori- 

 zon of experience expands. They are not inventions, but 

 descriptions of the state of a question. No man sees all 

 through a discovery at once." Thus Descartes's notion 

 of matter, and his explanation of motion, would be put 

 aside as trivial by a physiologist or a crystallographer of 

 the present day. They are not descriptions of the state 

 of the question. And yet a desire sometimes shows itself 

 in distinguished quarters to bind us down to conceptions 



1 Letter to Lange: * 'Geschichte des Materialismus, " zweite Aufl., vol. ii. 

 p. 521. 



2 "Nineteenth Century," September, 1878. 



