PROFESSOE VIRCHOW AND EVOLUTION. 393 



tinuity between us and our loftier brothers yet to 

 come. 



'We have guarded ourselves against saying that 

 the inferring of thought from material combinations 

 and arrangements would be an inference a priori. The 

 inference 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 aether knowing the physical 

 qualities of the medium 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 endea- 

 vour to pass by a similar process from the phenomena of 

 physics to those of thought, we meet a problem which 

 transcends any conceivable expansion of the powers 

 which we now possess. We may think over the subject 

 again and again, but it eludes all intellectual present- 

 ation. We stand at length face to face with the In- 

 comprehensible. 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. Cast- 

 ing 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 reached its very rim, a mighty 

 Mystery still looms beyond us. We have, in fact, made 

 no step towards its solution. And thus it will ever 



