92 PHYSIOLOGY CHAP. 



By means of the former, says Bichat in effect, these organisms are 

 constantly transforming into their own substance the materials 

 which they receive from outside, while they continually eliminate 

 the useless products of consumption ; by means of the latter, they 

 feel and perceive the external world, express their sensations, 

 perform voluntary movements under the influence of these, and 

 are able to express their desires and fears, their pains and 

 pleasures. 



Although modern science has established the unitary con- 

 ception of life, and has refuted the supposed antagonism between 

 the functions of plants and of animals, Bichat's general distinction 

 holds good as the basis of a rational classification. It is a fact 

 that the cardinal function of plants, taken as a whole, is the 

 synthetic building-up of organic matter, while that of animals is 

 its disintegration. 



On the other hand, it is undeniable that the higher animals 

 possess a system of organs and apparatus which essentially serve 

 the internal life of the body, by preparing and constantly re- 

 newing the pabulum common to all the living elements of which 

 it consists : while there is a second system which especially serves 

 the external life, by developing the potential energy of the living 

 matter. The first system recalls the predominance of anabolism 

 in plants, as compared with animals ; the second the predominance 

 of katabolism in animals, as compared with plants. 



Yet, if we attempt to determine exactly which organs and 

 apparatus compose the vegetative system, in distinction to those 

 of which the animal system consists, we encounter difficulties. 

 The embryological criterion, so often invoked in this connection, 

 i.e. the derivation of the different parts from one or other of the 

 three germinal layers, leads to no satisfactory result, since it is 

 now well established that tissues and organs are developed from the 

 external, and yet more from the middle, layer, which obviously 

 belong some to one system and some to the other. Clearly these 

 two systems do not represent two distinct and superposed organisms, 

 but rather two that are intimately connected and interdependent, 

 to be distinguished only by artificial means, contingent to a certain 

 extent on individual judgment and appreciation. 



It is the obvious function of the vegetative system, as a whole, 

 to keep constant the quantity and quality of the mass of blood, 

 from which is formed the lymph or plasma constituting the 

 common internal medium indispensable to the life of each vital 

 element. This system consists necessarily of the blood, of the 

 cardio- vascular apparatus by means of which it circulates, and of 

 the whole of the glandular organs and apparatus designed for its 

 constant renewal, elaboration, and cleansing. 



On the other hand, the function of the animal system is to 

 bring the animal through its sense organs into relation with the 



