THE ORGANICAL SCIENCES. 437 



circumstance which makes physiology an important part of our survey 

 of human knowledge is, that we have here a science which is con- 

 cerned, indeed, about material combinations, but in which we are led 

 almost beyond the borders of the material world, into the region of 

 sensation and perception, thought and will. Such a contemplation 

 may offer some suggestions which may prepare us for the transition 

 from physical to metaphysical speculations. 



In the survey which we must, for such purposes, take of the pro- 

 gress of physiology, it is by no means necessary that we should 

 exhaust the subject, and attempt to give the history of every branch 

 of the knowledge of the phenomena and laws of living creatures. It 

 will be sufficient, if we follow a few of the lines of such researches, 

 which may be considered as examples of the whole. We see that 

 life is accompanied and sustained by many processes, which at first 

 offer themselves to our notice as separate functions, however they may 

 afterwards be found to be connected and identified ; such are feeling, 

 digestion, respiration, the action of the heart and pulse, generation, 

 perception, voluntary motion. The analysis of any one of these 

 functions may be pursued separately. And since in this, as in all 

 genuine sciences, our knowledge becomes real and scientific, only in so 

 far as it is verified in particular facts, and thus established in general 

 propositions, such an original separation of the subjects of research is 

 requisite to a true representation of the growth of real knowledge. 

 The loose hypotheses and systems, concerning the connexion of differ- 

 ent vital faculties and the general nature of living things, which have 

 often been promulgated, must be excluded from this part of our plan. 

 We do not deny all value and merit to such speculations ; but they 

 cannot be admitted in the earlier stages of the history of physiology, 

 treated of as an inductive science. If the doctrine so propounded 

 have a solid and permanent truth, they will again come before us 

 when we have travelled through the range of more limited truths, and 

 are prepared to ascend with security and certainty into the higher 

 region of general physiological principles. If they cannot be arrived 

 at by such a road, they are then, however plausible and pleasing, no 

 portion of that real and progressive science with which alone our his- 

 tory is concerned. 



We proceed, therefore, to trace the establishment of some of the 

 more limited but certain doctrines of physiology. 



