OF RESPIRATION. 401 



object a motion to and from the organs of respiration. This will be 

 fully proved in the following division of this chapter. 



But from the arterial blood all, and especially the animal, organs, 

 derive that portion which is peculiarly theirs, and which is transformed 

 in them. Hence respiration is the first and chief cause of the florid 

 health as well as of the equal and uniform nourishment of all the organs 

 of the animal. The muscles and nerves particularly appear to derive 

 advantage from respiration, in consequence of the change thereby 

 occasioned in the blood*. Thence is it also that in animals with pre- 

 ponderant and highly developed organs of respiration muscular and 

 nervous activity prevails. That this is the case in insects, at least 

 with respect to their muscular power, requires no further proof; many 

 experiments and observations, and, indeed, daily experience, convinces 

 us of it. With what a monstrous expense of muscular power do not 

 these little creatures labour ! We have merely to reflect upon their 

 rapid and continued flight, upon the migrations of locusts, upon the 

 solid and compact woods which others destroy with their minute 

 mandibles, upon the powerful pressure which they are enabled to make 

 by their voluntary muscular force, when, for instance, a beetle is 

 taken in the hand, and it endeavours to free itself from its restraint. 

 With respect to their nervous activity, I will refer only to the sub- 

 tlety and strength of their sense of smell, particularly as this more than 

 any of the other senses stands in close connexion with respiration. 

 But their hearing is also acute, and, above all, their sight. Where 

 is there found such an accumulation of the organs of sight ? Where 

 such a relative size in any other class of animals ? Where so much 

 caution in the observation of their enemies, and patience in the com- 

 pletion of a once commenced undertaking? but which patience must be 

 attributed to the acute perception of their senses and their great mus- 

 cular strength. 



Hence respiration is, as well as the reception and digestion of food, 

 a chief cause of the undisturbed progress of all the animal functions ; 

 both go hand in hand, and the one is useless without the assistance of 

 the other. 



236. 



Another property which, if not produced by respiration alone, yet 

 stands in an intimate connexion with it, is the peculiar warmth found 

 in many animal bodies, especially in the mammalia and birds. Without 

 entering here upon the several explanations of the causes of this equal 



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