PHYSIOLOGY. 443 



interesting relations, especially in reference to the motion 

 of the vertebrae, ribs, limbs and jaws upon each other, 

 but these could not be here treated of in detail. 



2674. The acts of swimming, creeping, standing, 

 walking, running, leaping, climbing, and flying, do 

 not exhibit simply mechanical, but truly philosophical 

 moments. 



a. Bodily Motion. 



2675. Swimming can take place through simple con- 

 traction of the body, without locomotive members. It is 

 the continuation of the vesicle's first process of origination; 

 as in the Infusoria and Polyps. In the Worms and 

 Serpents it is effected by an undulating motion of the body, 

 whereby the water is struck with oblique surfaces ; there 

 it is fibrous motion. In the Holothuriae and many aquatic 

 larvae, it is a propulsion, effected by expelling water from 

 the anus, and thus by squirts, there being consequently 

 contraction of the body or arteriose straitening of the 

 sphincter muscles. In Fishes, swimming is a rowing or 

 remigial stroke, produced by lever-motion, together with 

 the oblique slap made by their tail. 



2676. Creeping is either a shortening of the body by 

 fibrous motion, as in the Snails, or an undulatory motion, 

 as in the Serpents. 



b. Pedal Motion. 



2677. Standing is the position of a lever "in equi- 

 librio," the creation of the proper centre of gravity. 



2678. Walking or running is an exchange or alterna- 

 tion of the equilibrium, a combination of standing and 

 creeping. 



2679. Leaping or hopping is a flight with the feet. 



2680. Climbing is an use of the feet as hands. 



c. Alary Motion. 



2681. Flying is lever-swimming in the air. It takes 

 place by means of aerial branchiae, namely, the wings in 

 Insects, and by the thoracic extremities in Birds, which 

 are also none other than animal branchiae. 



