INTRODUCTION. 39 



prospect of success, except in connection with the other. It is now coming to 

 be generally felt, that our fundamental ideas of healthy vital action must rest 

 on the knowledge of the structure, composition, and properties of the minutest 

 portions of the fabric; and in like manner, our fundamental notions of the 

 changes in which disease essentially consists, are coming to rest more and more 

 upon the detection of the perversions which the actions of these parts undergo, 

 and of the minute alterations of structure and composition which they involve. 

 . It is, in fact, in the detection of those first departures from the normal actions 

 which frequently constitute the essence of a disease, and in the determination 

 of the causes to whose operation they are referable, that Medical Science is at 

 present making the greatest progress ; and it would not be difficult to show, that 

 this progress is intimately connected with the advance of Physiology. To say 

 that it is impossible to interpret the phenomena of disease with any probability 

 of correctness, impossible to apply remedies with a reasonable expectation of 

 success impossible, therefore, to practise the healing art as it ought to be prac- 

 tised unless we are acquainted with the normal or healthy action of the system, 

 might seem a truism ; and yet, however self-evident the truth of the assertion, 

 it is very far from having the weight which it ought to possess. The phenomena 

 of Disease have been isolated from those of Health, as if they belonged to quite 

 a distinct category, and were dependent upon a set of causes altogether dissimilar. 

 It has been too much lost sight of, that every diseased action is but a perversion, 

 by excess, by diminution, or by depravation, of some natural function ', and that 

 only through an acquaintance with the latter can the former be understood 

 (otherwise than in a merely empirical fashion), either as to its cause, its nature, 

 or its tendencies. It has been assumed by some Pathologists, that Physiology 

 ought to furnish a set of direct rules for the treatment of disease; and, as it 

 cannot rightly profess to furnish these, it has been set down by others as having 

 no practical value whatever. Whereas the real Medical Philosopher rather looks 

 to Physiology as affording guidance in the pursuit of those rules, by furnishing 

 a clue to his interpretation of symptoms, by pointing out the direction in which 

 he may look for remedies, and by letting in, here and there, a beam of light 

 that shall guide him through the intricacies of his search. In fact, it is with 

 this constant but unobtrusive assistance from Physiology, that the Pathologist 

 advances in his career of research ; and hence it is just where our Physiological 

 knowledge is most precise, and its generalizations most comprehensive, that our 

 Pathological information is most advanced and most fruitful in practical results. 

 It may be taken, indeed, as a general fact, that those Arts, or collections of 

 rules for a given purpose, are the most perfect in their application, which are 



