310 ANIMAL NATURE AS A WHOLE. [iii. 



possibly be endowed with cerebral forces^ be a plant or an 

 animal. Hence the confusion of ideas, caused by the researches 

 on decapitated animals, moved solely by the vis nervosa, — by 

 the phenomena of anencephalous infants bom alive — and by 

 animals so constituted by nature, as to live without head or 

 brain, and which manifest no traces of mind; regarding all 

 which no definite opinion can be stated. If, however, the above 

 general distinction be adopted, no difficulty arises in such cases ; 

 for, although entirely without conceptions, all these organisms 

 are regulated by external impressions, in a way wholly different 

 from plants, and according to wholly different laws. Now, 

 since we recognise the existence of the vis nervosa of external 

 impressions in animal machines [the brain and nerves], and 

 know that it is adapted to sentient animals, and excites in them 

 the same movements, according to the same peculiar laws as 

 external impressions excite in these organisms; and since we 

 find machines in the latter, which are very similar to the 

 animal machines [brain and nerves] of sentient animals, we 

 can positively decide, that all these organisms are moved 

 animally by nature, by means of animal machines, and that 

 they also belong to the class of animal bodies. 



601. Still, as has been said, the line of distinction is always 

 indefinite, and the limits of the animal and vegetable kingdoms 

 run so into each other, that they cannot be defined. The 

 fault, however, is not in the want of grounds of distinction, 

 but in the difficulty of discovering them in many cases. The 

 movements excited in the sensitive plant by a touch, leads us 

 to the conclusion that it is a zoophyte; so fixed is the principle 

 in us, that an organism must be an animal which is moved by 

 certain impressions — not according to physical and mechanical 

 laws — but according to the laws of movement in animals. But 

 these movements are neither sentient actions nor nerve-actions, 

 for upon investigating the structure of the leaf, it is found that 

 the closing of the leaves is simply a mechanical action, excited 

 by a touch. 



602. The question may arise, however, whether a body may 

 not be animal in its nature, and yet not be an animal ; as, for 

 example, in the case of a decapitated animal. A man, deprived 

 of his limbs, is not the less a man ; and so if the vis nervosa 

 continue in a mutilated creature, it is still an animal. Besides, 



