CONCLUDING REMARKS. 245 



the animal body, we need only refer to what has been stated in 

 reference to this subject in the first volume, since they take a less 

 important part in the more general functions of life. 



Now that we are approaching towards the termination of the 

 general considerations of the arrangement of the most important 

 chemical substrata observable in the metamorphosis of matter, we 

 are forcibly reminded of the ancient saying of Aristippus, that the 

 most probable is often untrue, and the most improbable true. If 

 we are correct in forming a low estimate of the amount of our positive 

 knowledge, we ought to exercise extreme caution in the selection 

 of the principles by which we regulate our judgment regarding 

 the positive results of our observations and experiments. In our 

 application of chemistry to physiology, we must be especially 

 mindful of the fact that most of the fundamental propositions 

 which at the present time have attained to a general recognition 

 in chemistry, by no means possess such a degree of scientific, or 

 rather of logical, exactness as to place them beyond all dispute. 

 We must not forget that chemistry, like medicine and theology, 

 although perhaps in a more limited degree, possesses a dogmatism 

 of its own. How many of the modes of consideration which are 

 now valid in scientific chemistry, are the mere provisional modes 

 of expressions for certain groups of phenomena, whose analogy is 

 obvious, but whose internal connection and relations of causality 

 are alike incomprehensible and unknown ! A chemist of the old 

 school would be indignant if any one were to hint at the faintest 

 doubt of the correctness of the hypothesis that chemical com- 

 binations can only be effected in accordance with definite 

 numerical proportions, or should venture to assert that gradual 

 metamorphoses, which are alike independent of mathematical laws, 

 and perfectly foreign to the ordinary chemical affinities, might 

 run their course in the highest spheres of vitality. Yet every 

 chemist who regards chemistry and physics as inadequate for the 

 science of life, and on that account deems it necessary to call vital 

 forces to his aid, must of necessity admit the cogency of these 

 doubts ; for experiments have alike failed to show that albuminous 

 and histogenetic substances generally are constituted in accordance 

 with perfectly definite numerical relations, or that any supervising 

 agent has been appointed to control the economy of the living 

 organism. 



We need not, however, encroach upon the sphere of vitality to 

 show the uncertainty and purely dogmatic nature of many of the 

 more general principles of chemistry. Many principles which 



