PROFESSOR VIRCHOW AND EVOLUTION 411 



be no absolute breacb of continuity between us and our 

 loftier brothers yet to come. 



"We have guarded ourselves against saying that the 

 inferring of thought from material combinations and ar- 

 rangements would be an inference d priori. The infer- 

 ence meant would be the same in kind as that which the 

 observation of the effects of food and drink upon the mind 

 would enable us to make, differing only from the latter 

 in the degree of analytical insight which we suppose 

 attained. Given the masses and distances of the planets, 

 we can infer the perturbations consequent on their mutual 

 attractions. Given the nature of a disturbance in water, 

 air, or ether— knowing the physical qualities of the me- 

 dium we can infer how its particles will be affected. In 

 all this we deal with physical laws. The mind runs with 

 certainty along the line of thought which connects the 

 phenomena, and from beginning to end there is no break 

 in the chain. But when we endeavor to pass by a similar 

 process from the phenomena of physics to those of thought, 

 we meet a problem which transcends any conceivable ex- 

 pansion of the powers which we now possess. We may 

 think over the subject again and again, but it eludes all 

 intellectual presentation. We stand at length face to face 

 with the Incomprehensible. The territory of physics is 

 wide, but it has its limits from which we look with vacant 

 gaze into the region beyond. Let us follow matter to its 

 utmost bounds, let us claim it in all its forms — even in 

 the muscles, blood, and brain of man himself — as ours to 

 experiment with and to speculate upon. Casting the term 

 * vital force' from our vocabulary, let us reduce, if we can, 

 the visible phenomena of life to mechanical attractions 

 and repulsions. Having thus exhausted physics, and 



