x INTRODUCTION. 



of the common flea or the lobster, the last of which .has to leap against the reaction of 

 water, it would be almost from jungle to jungle, or from mountain to mountain ; and if the 

 strongest-shelled tortoise were to fall from a height proportional to that from which many of 

 the invertebrated animals can fall with perfect impunity, it would be dashed to pieces. 



From all that we can observe, we have reason to conclude that the nervous or sensatory 

 system admits of the highest degree of animal organisation, the one which is the farthest re- 

 moved from the common properties of dead matter ; and in proportion as that system is more 

 developed and predominant, the functions of the animal become more varied, but individually 

 less capable of effort, and altogether less capable of endurance. A 'very slight wound causes 

 death in the mammalia and birds ; and though the reptiles and fishes can recover from severe 

 lacerations, they are all suceptible of being wounded to death ; but when we come to what 

 may be considered the inferior tribes of the invertebrated animals, where there are few 

 functions, few organs, and nothing which can be positively pronounced to be a distinct 

 nervous system the entire animal being little else than a skin which can feel we find that 

 no cutting, and hardly even pounding in a mortar, can put the creature wholly to death. 

 Still we do not know enough of the functions of those animals, or of the developments of 

 the different systems in the different races of animals, to enable us to arrive at any certain 

 conclusions with regard to the relations which the intensities of actions in those several 

 systems have to each other, or to the power of endurance or of action in the animal generally, 

 or the other systems which make up its organisation. 



Hence it is necessary to observe great caution in assigning the energy of one part of the 

 organisation to another part, or of pronouncing any one of the systems of which the 

 organisation is made up as being the sole, or even the chief, seat of animal life. Even from 

 ourselves, where, as we have feeling added to observation, our knowledge should be most 

 perfect, we can conclude nothing without a stretch of theory which does violence to the truth. 

 The circulating, the nervous, and the alimentary systems have at times been each regarded 

 as the seat of animal life in man, (not as the locality of the mind, for that mind can have 

 physical locality, while from its very nature it can have no physical extension, involves a 

 contradiction in terms,) but of our animal life without any reference whatever to the mind. 

 In fact, those principal systems seem to be all pretty equally the seats of life, as there are 

 peculiar injuries which, if done to any of the three, will extinguish it with equal rapidity. 



Indeed, the safest conclusion is that the life is in the organisation rather than in the 

 organs ; and as we cannot subject that to experiment, we can safely carry our theories no 

 farther than the facts which actually come under our observation. Of this much we are 

 certain, both from what has been mentioned of the invertebrated animals, and from what we 

 observe in the vertebrated ones, that the perfection of the nervous system is not in proportion 

 to the motive one, and, perhaps, sometimes not even to perception itself, in at least some of 

 its forms, whatever it may be in others. The nervous system in the eagle and the vulture is 

 much less perfect than in the mammalia ; and yet the vision of the one, and the means, 

 whatever they may be, by which the other finds out its food at very long distances, are far 

 more acute than any similar capacity in the more perfect class. The return of bees to their!/ 

 hives and other resting places, and countless other habits of invertebrated animals, which 

 cannot depend upon any thing at all analogous to the operation of our senses, are well 

 calculated to teach us caution in coming to those conclusions, respecting the animals that 

 differ greatly from ourselves in their organisation, to which we are too apt to be betrayed 

 when we begin the study of zoology. 



The fact of being invertebrated serves to separate this division of the animal kingdom from 

 the former, but as it is a negative, it cannot be made the foundation of a positive definition ; 

 and the animals differ so much from each other, that it is not easy to write any thing general 



