OF ANIMALS. 31 



be executed by digestion, for the animal could not at the same 

 time possess the power of locomotion, and be fixed; genera- 

 tion in this case is sexual. In proportion as each order of 

 functions becomes more complicated, the organs superadded 

 to those, whose existence is more general, hold the for- 

 mer under their control. Thus, for instance in the order of 

 the nutritive functions, the circulation, and in the latter, the 

 action of the heart, which is not as common as the other nu- 

 tritive phenomena, keep, when they exist, all the others under 

 their influence. In the same manner, in the animal functions, 

 the action of the nervous centres holds in subjection those 

 phenomena, whose existence is more generally met with in 

 organized beings. The animal functions hold under theirs 

 all the nutritive and reproductive ones, but these latter, in 

 their turn, keep the former in a similar state; the organs of 

 animal functions having to be nourished, in order to fulfil 

 their own, and these latter inducing the exercise of the organs 

 of the vegetative functions. So that, in animals whose orga- 

 nization is very much developed, life seems essentially to re- 

 sult from the reciprocal action of the central organ of the ve- 

 getative functions, and from the principal organ of the animal 

 functions, from the circulation and the nervons action, or in 

 other words, from the action of the blood on the nervous sys- 

 tem, and from the nervous system on the organs which propel 

 the blood. The other phenomena maintain these two princi- 

 pal actions, which may be considered as the two essentially 

 vital functions of animals. 



16. To all these characters, the first very general and 

 common, and the second much less so, we must add the disor- 

 ders of the organization, and the phenomena of life, i. e. dis- 

 eases much more frequent in animals than in vegetables; and 

 the reason of this may be easily found in the complication of 

 their organization, in the concatenation of all the parts with 

 each other; and in the operation of central and predominating 

 organs, the action of which can not be disturbed without the 

 whole economy suffering by it. Hence the study of the causes 

 and external bodies which influence the animal organization 



in a hurtful or beneficial manner, and the art of preserving or 

 6 



