CHEMISTRY AND PHYSICS IN RELATION 



nature, but also, those of animal and vegetable life, are peculiar to themselves, 

 stand in certain relations to each other, and depend upon certain causes ; and if 

 farther, it be true that it is only by a knowledge of these causes or conditions that 

 wfc can gain a clear insight into the existence of organic processes, then must tht 

 investigation of the reciprocal dependence and the conditions of the phenomena of 

 Jife, be regarded as the most important department of physiology. 

 j The explanation of many natural phenomena, requires, in most cases, nothing 

 more than an acquaintance with the relaJiojLuf._dependence in which they stand, 

 one to the other. 



The knowledge of these relations is attainable in every branch of natural 

 investigation by the extension of experience, and by correctness of observation ; 

 and there can be no question that, at some future time, as chemistry loses the 

 character of an experimental art, so will physiology be capable of ranking as a 

 deductive science. 



COURSE OF INVESTIGATION. 



If it follow, according to the course of natural investigation, that general laws 



must be preceded by those that are merely special, and it be granted that a just 



conception of life cannot be acquired without a thorough knowledge of the 



] organim in all its parts, both with reference to the functions of individual organs 



I in themselves, and their ^girUi^Ljlependence, including the consideration of the 



^relation of form to organic matter ; tKen it will not be denied that we are still 



most widely removed from the possession of a general formula, embracing the 



comprehension of life, and the knowledge of the causes and connections existing 



in natural phenomena. So remote is this object, that there are many who still 



regard the probability, or even possibility of the attainment of such general laws 



in physiology, as purely chimerical ; while most persons are unable to distinguish 



psychical from corporeal phenomena, or the idea of vital power from the form of 



living organs. 



PRECONCEIVED VIEWS, AN IMPEDIMENT TO INVESTIGATION, 



A man even of the most cultivated mind cannot wholly emancipate himself 

 from the dominion of those laws, on which his powers of comprehension are 

 dependant. If the daily experience of a prolonged period constantly show him 

 two phenomena or facts, apparently closely connected together, if he learn that, 

 for centuries, they have been considered inseparable, and if he have never, either 

 by accident or design, been led to consider each individually, he becomes gradually 

 incapable, in spite of the greatest exertion to the contrary, of considering them 

 apart, until at length his mind refuses to admit the very assumption of any difference 

 existing in the nature of the phenomena observed. 



Innumerable instances testify that even the most accurate observers of their age 

 have regarded certain facts or representations as impossible, simply because their 

 power of comprehension was unable to receive them ; while their successors have 

 not only comprehended them, but what is far more, have universally received them 

 as incontestible truths. 



Men of the clearest discernment, who were raised far above ordinary ideas, 

 were yet unable to understand that the force of gravity acts with an upward 

 instead of a downward tendency, or that the sun from its vast distance could exer- 

 cise any influence upon the earth, or the earth upon the moon. Even the great 

 Leibnitz rejected the Newtonian theory, because he could not regard it as possible 

 that the planets could maintain a motion in a curved line around one common 

 centre, without the agency of some continuously acting mechanism ; since accor- 



