OF ANIMALS. 



i^ pro(iu0ed.: By motions of this kind, the most im- 

 portant, functions of the system are performed, as the circu- 

 lation of the blood; the digestion of food; the peristaltic 

 motion of the intestines; the absorption of the chyle; its 

 transmission from the abdomen into the subclavian vein, &c. 

 Yet none of these operations has any dependence upon our 

 will or inclinations.' Together with the action of the lungs 

 in respiration, they have received the denomination of vital 

 and involuntary motions, because most of them go on without 

 any conscious exertions of the intellectual principle. If such 

 a variety of nice and complicated movements had been left 

 to the determination and direction of our minds, they must 

 necessarily have occupied too much of our attention ; and 

 many of them would infallibly have been neglected during 

 sleep, when consciousness is almost totally suspended. But 

 Nature in her operations is always wise. She has given to 

 mari, and other animals, the direction of no movements but 

 what are easily performed, contribute to pleasure and health, 

 and enable them to acquire food corresponding to the struc- 

 ture of their bodies and the elements in which they live. 



It would be foreign to the design of this work, and ill 

 suited to those to whom chiefly it is intended to be useful, to 

 enter into the rationale of animal motion ; to mention the 

 number, insertion, and direction of the muscles employed in 

 moving the different parts of animated bodies ; or to account 

 for the modes by which animals walk, leap, fly, swim, creep, 

 &/c. Such discussions would not only require a volume, but a 

 thorough acquaintance with all the depths of anatomical and 

 mathematical knowledge. What follows, therefore, will con- 

 sist of some desultory observations ; and the subject will be 

 concluded by enumerating a few examples of movements pe- 

 culiar to certain animals. 



' Every class of animals has in general its limited sphere of 

 motion, from which the individuals belonging to it seldom 

 depart. Thus quadrupeds are constructed so as to move 

 with the greatest facility upon the earth, birds in the air, and 

 fishes in the water ; yet there are exceptions with regard to 

 all these classes. The bat is furnished with wings, and can 

 traverse the air with as much facility as many birds; the 

 ostrich, though furnished with wings, is confined to the earth, 

 and can only walk or run ; whilst the flying-fish has fins so 

 large, that it is capable of raising itself out of the water, and 

 maintaining a flight for some time in the air. 



' The limbs of animals are always adapted to the particular 



