224 GENERAL VIEW OF THE FUNCTIONS. 



duction of food into the stomach, again, is dependent, like the actions of Re- 

 spiration, upon the operations of the muscular apparatus and of a part of the 

 nervous centres; and the previous acquirement of food necessarily involves 

 the purely Animal powers. Now it will serve to show the distinction between 

 these powers, and those which are merely subservient to Organic life, if we 

 advert to the case, which is of no unfrequent occurrence, of a human being, 

 deprived, by some morbid condition of the brain, of all the powers of Animal 

 life, Sensation, Thought, Volition, &c.; and yet capable of maintaining a 

 vegetative existence, all the organic functions going on as usual, the morbid 

 condition not having affected the division of the nervous system, that is con- 

 cerned in the movements on which some of them depend. It is evident that 

 we can assign no definite limits to such a state, so long as the necessary food 

 is placed within reach of the grasp of the muscles, that will convey it into the 

 stomach ; as a matter of fact, however, it is seldom of long continuance ; 

 since the disordered state of the brain is sure to extend itself, sooner or later, 

 to the rest of the nervous system. This condition may be experimentally 

 imitated, however, by the removal of the brain in many of the lower animals, 

 whose bodies will sustain life for many months after such a mutilation; but 

 this can only take place when that food is conveyed by external agency 

 within the pharynx, which they would, if in their natural condition, have ob- 

 tained for themselves. A similar experiment is sometimes made by Nature 

 for the Physiologist, in the production of foetuses, as well of the human as of 

 other species, in which the brain is absent ; these can breathe and suck and 

 swallow, and perform all their organic functions ; and there is no assignable 

 limit to their existence, so long as they are duly supplied with food. Hence 

 we may learn the exact nature of the dependence of the Organic functions 

 upon those of purely Animal life ; and we perceive that, though less imme- 

 diate than it is upon the simple organic operations of the nervous and muscu- 

 lar systems, it is not less complete. On the other hand, the functions of 

 Animal life are even more closely dependent upon the Nutritive actions than 

 are those of organic life in general ; for many tissues will retain their several 

 properties, and their power of growth and extension, for a much longer pe- 

 riod after a general interruption of the circulation, than will the Nervous 

 structure ; which is, indeed, instantaneously affected by a cessation of the due 

 supply of blood, or by the depravation of its quality. 



267. It is of little consequence, then, with which group of functions we 

 commence the detailed study of the phenomena, which in their totality make 

 up the life of Man. In viewing him merely as one of the widely-extended 

 group of organized beings, it would be natural to commence with those phe- 

 nomena which are common to all ; and to make, therefore, the Organic func- 

 tions the first object of our consideration. On the other hand, regarding Man 

 as a being in some degree isolated from all these by his peculiar character- 

 istics, it seems right to inquire into the latter in the first instance; more 

 especially as, in a general view of his life, these occupy the most prominent 

 place. It will be necessary, however, previously to entering upon them, to 

 take a more detailed survey than we have hitherto done, of the vital opera- 

 tions performed by his several organs, and of their connections with each 

 other. We shall commence with those of Vegetative Life. 



2. Functions of Vegetative Life. 



268. It is one of the most peculiar characteristics of Organized structure, 

 that its elements have a constant tendency (under ordinary circumstances at 

 least) to separate into more simple combinations ; and although it has been 

 ordinarily considered, that their living state prevents such a change, and that 



