BOOK I. 



GENERAL PHYSIOLOGY, 



CHAPTER I. 



ON THE NATUKE AND OBJECTS OF THE SCIENCE OF PHYSIOLOGY. 



1. THE general distribution of the objects presented to us by external 

 nature, into three kingdoms the Animal, the Vegetable, and the Mine- 

 ral, is familiar to every one ; and not less familiar is the general distinc- 

 tion between living bodies, and dead inert matter. True it is, that we can- 

 not always clearly assign the limits which separate these distinct classes 

 of objects. Even the professed Naturalist is constantly subject to per- 

 plexity as to the exact boundary between the Animal and the Vegetable 

 kingdoms ; and the distinction between Animal and Vegetable struc- 

 tures, on the one hand, and Mineral masses on the other, or between 

 living bodies, and aggregations of inert matter, is by no means so 

 obvious in every case, as to be at once perceptible to the unscientific 

 observer. Thus, a mass of Coral, if its growing portion be kept out of 

 view, or a solid Nullipore attached to the surface of a rock, might be 

 easily confounded with the mineral bodies to which they bear so close a 

 resemblance ; and a minute examination might be required to detect the 

 difference. Nevertheless, a well-marked distinction does exist, between 

 the organized structures of Plants and Animals, and the inorganic 

 aggregations of Mineral matter ; as well as between the condition of 

 a living being, whether Animal or Plant, and that of dead or inert 

 Mineral bodies. It is upon these distinctions, which are usually obvious 

 enough, that the sciences of ANATOMY and PHYSIOLOGY are founded ;: 

 these sciences taking cognizance, the former, of those structures which 

 are termed organized, and the latter, of the actions which are peculiar 

 to those structures, and which are distinguished by the term vital. It 

 will be desirable to consider, in a somewhat systematic order, the prin- 

 cipal ideas which we attach to these terms ; as we shall be thus led most 

 directly to the distinct comprehension of the nature and objects of Phy- 

 siological science. 



