95 



Report on Animal Physiology ; comprising a Review of the 

 Progress and Present State of Theory, and of our Informa- 

 tion respecting the Blood, and the Powers which circulate it. 

 By WiLLtAM Clark, M.D., F.R.C. F.G.S. F.C.P.S., 

 late Fellow of Trinity College, and Professor of Anatomy 

 in the University of Cambridge. 



That physiology should have been a science slow and uncertain 

 in its progress is scarcely surprising, when we consider how ex- 

 tensive are its objects. It pretends to nothing less than to explain 

 the phaenomena of living nature, — the conditions upon which 

 they depend, — the laws by which they are governed. Hence, it 

 inquires not only into the relations of every component part of 

 an individual to each other and to the whole, but also, as far as 

 is possible, into the mutual relations of all living things to each 

 other, and to the rest of the world. In its useful application, 

 therefore, it is the foundation of agriculture, of husbandry, of 

 medicine. Intentions thus ample can only be fulfilled when all 

 particular sciences have gained their consummation. In earlier 

 aeras it was included in those ideal assumptions, from which, as 

 from axioms, it was conceived that all the pheenomena of nature 

 might be deduced ; whilst, in later times, the attempt to treat it 

 merely as a branch of the prevailing chemical or mechanical phi- 

 losophy of the day favoured its advance in particular directions 

 only, and with very confined conceptions of its nature and extent ; 

 as if any two of these sciences had yet ascertained, by means of 

 their ovra generalizations, a common proximate cause of their 

 phaenomena ; or, as if particular sciences were something else 

 than constructions of the intellect to explain phaenomena be- 

 tween which similarity has been established. 



Physiology, as a positive science, can only be founded in obser- 

 vation and experiment; and the value of these depends, as in other 

 cases, not less upon the patience, the circumspection, the dispas- 

 sionate, and unprejudiced character of the observer than upon his 

 scientific and mental elevation. The multitude of physiological 

 experiments daily accumulated, tells us how easily they may be 

 made ; the facility with which one set of experiments so frequent- 

 ly supersedes a former, how difficult it is to make experiments of 

 real value. So numerous, indeed, are the conditions with which 

 every vital phaenomenon is complicated, that the effect may really 

 be referrible to one or more of these entirely diflferent from that 

 to which the experimenter has referred it. And, since it is im- 



