TO PHYSIOLOGY AND PATHOLOGY. 



ding to him in the absence of a propelling power, the body must fly off at a 

 tangent to its orbit. 



Starting from the general proposition that a body qan exercise no influence upon 

 a point, with which it is not in contact, the Newtonian theory of gravitation was 

 rejected ; and the fact now become familiar to the mere schoolboy, that the power 

 of gravitation is active at boundless distances without any influencing material 

 agent, appeared even to men of the noblest intellect to contain so great a contra- 

 diction, that rather than receive it, they maintained the probability of the strange, 

 and unfounded creations of their own fancy. 



There are many theories in mechanics and physics, which, although we know 

 to have been regarded as the great discoveries of their age, and the results of the 

 most patient and laborious investigations, appear to us now so true and obvious, 

 that if we did not possess the history of their gradual development, it would seem 

 incredible that a doubt of their truth could ever have been entertained by any 

 individual in any age. 



The simple position that a body once put in motion, could traverse space, for- 

 ever pursuing with unvarying velocity the same direction, appeared so opposite to 

 common and evident experience that the recognition and establishment of its truth 

 met for a long period with the greatest opposition. 



That two chemico-active bodies can form a combination of definite unchange- 

 able properties, through their union in indefinite or unlimited proportions, appears, 

 even to our sound powers of comprehension to be untenable. 



The comprehensive has, as we have shown, nothing to do with the apparent, 

 but is dependant upon the condition of our mental development. If the uniting 

 link that associates a fact with the usual counse of our ideas be wanting, the fact 

 itself will appear devoid of truth antl comprehensibility. This is one of the 

 greatest impediments that stands in the way of the application of chemistry to 

 psychology, and of a simple consideration of chemical discoveries on the part of 

 many physiologists ; and if to this be associated, as in pathology, the assumption 

 of facts on experience, the correctness of which has no other foundation than the 

 opinion of many centuries, and if, in these branches of science, the mode of arriv- 

 ing at conclusions and deductions be not changed, there is no hope as yet, that 

 chemistry, with all her advances, will ever be able to render any essential aid to 

 physiology and pathology ; while it is alike impossible for either of these sciences 

 to attain to any scientific basis, without the co-operation of chemistry and physics. 

 While no one doubts the necessity of this co-operation, there is little unity of 

 sentiment regarding its practical application. 



PHYSIOLOGY AS A DEDUCTIVE SCIENCE. 



The opinion that every empirical science, including physiology, may, in the 

 course of time, acquire the character of a deductive science, seems to require no 

 confirmation; and it must be immaterial whether this position be attained by bor- 

 rowing from other sciences: as for instance, in the case of astronomy, which owes 

 its scientific basis to its partial incorporation with the theory of motion. 



INVESTIGATION PURSUED ACCORDING TO PHYSIOLOGICAL LAWS. 



If we bear in mind that, as no occurrence in the world, so also no phenomenon 

 of nature, either in the animal or vegetable kingdom, can appear without standing 

 in relation to, or as the immediate result of another, that has preceded it ; (as the 

 present condition of a plant or animal is dependent upon certain pre-existing con- 

 ditions ;) it is clear, that if all the causes that affect one condition and their in- 

 fluence upon time and space, with their properties, are known to us, we shall be 



