26 CONNECTION OF PHYSIOLOGY WITH 



in whom such a pulse would be equivalent to one of 140, in a person whose 

 circulation was in health of the average rapidity. Thus an abnormal state in 

 any individual can frequently be ascertained only by comparison with his 

 normal condition. This is a difficulty from which we can never hope to make 

 a complete escape ; for it is the peculiar character of living beings, to exhibit 

 such variations in their phenomena, resulting from the number of concurrent 

 causes which are involved in the production of these ; a slight alteration in 

 any one of which will most seriously affect the general result. Upon the 

 distinction between normal and abnormal life, however, is founded that of the 

 two sciences Physiology and Pathology. These are very closely related to 

 each other ; and neither can be pursued with the prospect of complete success, 

 except in connection \vith the other. 



3. The relation between the sciences of Physiology and Pathology on the 

 one hand, and the various departments of the Ars Medendi on the other, may 

 be shown within a brief compass ; and it is perhaps desirable to point them 

 out here, in order to place the importance of these sciences in its proper light. 

 Science must strictly be said to consist of general principles, embodying the 

 phenomena which present themselves to the observer, in any particular de- 

 partment of observation ; and a science is perfect, in so far as its collection of 

 facts is reducible to these general laws, the ascertainment of which enables us 

 to extend our knowledge of similar facts. An Art is, properly speaking, the 

 application of a science to practical purposes, consisting of a set of rules de- 

 duced from its principles ; and its perfection will be exactly proportional to 

 that of the science upon which it rests. The most perfect of all sciences is 

 astronomy ; all its leading phenomena may be reduced to one general prin- 

 ciple ; and phenomena, previously unobserved, have been predicted as the 

 necessary results of that principle. The Art of Navigation is a collection of 

 rules, framed by those who were profoundly conversant with the principles of 

 the science ; but capable of being employed by those whose knowledge 

 extends no further than to the mode of applying them. When, however, the 

 science has not this degree of perfection, the art has not this independent 

 character. In Chemistry, for example, many principles of high generality 

 have been attained ; and yet unknown phenomena cannot be predicted from 

 them with certainty (in a great variety of cases at least), owing to the number 

 of other conditions by which they may be affected. Hence no art founded 

 upon this science can be supplied with any other than very limited rules. In 

 the case of dyeing, for example, great improvement has been effected by 

 chemical knowledge ; but the greater part of its rules are empirical, that is to 

 say, founded on a limited induction, not comprehended in more general prin- 

 ciples, and therefore quite uncertain in their results. Thus, if a new Animal 

 or Vegetable dye were discovered, the modes of fixing- and discharging it, and 

 of varying its shades of colour, w r ould have to be determined by experiment, 

 before it could be brought into advantageous employment. We can neverthe- 

 less imagine, and (from the recent great advance in Organic Chemistry) in 

 some degree anticipate, the period, when chemical science shall be so far 

 advanced, that a simple analysis of the material (supplying data corresponding 

 to the solar or lunar observations of the navigator) may enable the manufac- 

 turer, by a reference to his code of rules, to avail himself to the fullest extent 

 of its capabilities, without being himself aware of the principles upon which 

 those rules are founded. 



4. An Art, then, will be scientific or empirical (that is, its rules will be 

 based upon general principles, or upon induction from a limited experience), 

 in proportion to the comprehensiveness of the laws that have been attained in 

 the Science on which it rests. This distinction, however, has nothing to do 

 with the certainty or uncertainty of its application in particular instances. 



