288 SCIENCE OF AGRICULTURE. Part IL 



1901. In animnls nnlh many feet, as the Myriopoda, walking is performed by so unifoma 

 a motion, that the body may be said to glide along the surface. 



1902. In animals with four feet, " each step is executed by two legs only ; one belonging to the fore 

 pair, and the other to the hind pair; but sometimes they are those of the same side, and sometimes those 

 of opposite sides." {Cuvier's Comparative Anatomy, lect. vii, a, 1.) The latter is that kind of motion in 

 horses, which grooms term apace. The right fore-leg is advanced so as to sustain the body, which is 

 thrown upon it by the left hind-foot, and at the same time, the latter bends in order to its being moved 

 forward. While they are off the ground, the right hind-foot begins to extend itself, and the moment 

 they touch the ground, the left fore-foot moves forward to support the impulse of the right foot, which 

 likewise moves forward. The body is thus supported alternately by two legs placed in a diagonal manner. 

 When the right fore-foot moves, in order to sustain the body, pushed forward by the right hind-foot, the 

 motion is then called an amble. The body, being alternately supported by two legs on the same side, is 

 obliged to balance itself to the right and left, in order to avoid falling; and it is this balancing movement 

 which renders the gait so soft and agreeable to women and persons in a weak state of body. {Cuvier's 

 Camp. Anat., lect. vii.) 



1903. The serpentine motion consists in bringing up the tail towards the head by bending the body into 

 one or more curves, then resting upon the tail, and extending the body, thus moving forward, at each 

 step, nearly the whole length of the body, or one or more of the curves into wliich it was formed. Among 

 the MoUusca, and many of the annulose animals, the same kind of motion is performed by alternate 

 contractions and expansions, laterally and longitudinally of the whole body, or of those parts which 

 are appropriated to progressive motion. 



19W. A mode of tnoving analagous to walking, is performed by animals who have suckers, and is 

 exemplified in the leech, which at every step advances nearly the whole length of its body. 



1905. In the action of leaping, the whole body rises from the ground, and for a 

 short period is suspended in the air. It is produced by the sudden extension of the 

 limbs, after they have undergone an unusual degree of flexion. The extent of the leap 

 depends on the form and size of the body, and the length and strength of the limbs. The 

 Myriopoda are not observed to leap. Many of the spiders and insects leap with ease 

 forwards, backwards, and laterally. In those which are remarkable for this faculty, 

 the thighs of the hind-legs are in general of uncominon size and strength. Among 

 reptiles the leaping frog is well known, in opposition to the crawling toad. Among 

 quadrupeds, th6se are observed to leap best, which have the hind legs longer and thicker 

 than the fore-legs, as the kangaroo and the hare. These walk with difficulty, but leap 

 with ease. 



1906. Serpents are said to leap, by folding their bodies into several undulations, which they unbend all 

 at once, according to the velocity they wish to give to their motion. The jumping maggot, found in 

 cheese, erects itself upon its anus, then forms its body into a circle, bringing its head to the tail; and, 

 having contracted every part as much as possible, unbends with a sudden jerk, and darts forward 

 to a surprising distance. Many crabs and Podurae bend their tail, or hairs which supply its i)lace, 

 under their belly, and then, suddenly unbending, give to the body a considerable degree of progressive 

 motion. 



1 907. Flying. Flying is the continued suspension and progress of the whole body in 

 the air, by the action of the wings. In leaping, the body is equally suspended in the 

 air, but the suspension is only momentary ; in flying, on the contrary, the body remains 

 in the air, and acquires a progressive motion by repeated strokes of the wings on the 

 surrounding fluid. The centre of gravity is always below the insertion of the wings in 

 the bodies of flying animals to prevent them from falling on their backs, but near that 

 point on which the body is, during flight, as it were suspended. The action of flying is 

 performed by animals belonging to different classes. Among the Mammalia, bats dis- 

 play this faculty, by means of wings, formed of a thin membrane extending between 

 the toes, which are long and spreading, between the fore and hind legs, and between the 

 hind legs and the tail. In birds, the wings, which occupy the place of the anterior 

 extremities in the Mammalia, and are the organs of flight, consist of feathers, which are 

 stronger than those on the body, and of greater length. Among reptiles, the flying lizard 

 may be mentioned, whose membranaceous wings, projecting from each side of the body, 

 without being connected with the legs, enable it to fly from one tree to another in search 

 of food. A few fishes are likewise capable of sustaining themselves for a short time by 

 means of their fins ; these are termed flying fish. Spiders are able to move in the air by 

 means of their threads. 



1 908. Swimming is the same kind of action in water, as flying is in air. The organs 

 which are employed for this purpose resemble the oars of a boat in their mode of action, 

 and in general possess a considerable extent of surface and freedom of motion. Swim- 

 ming, however, is not confined to those animals which are furnished with oars or 

 swimmers. Many animals move with ease in the water by means of repeated undulations 

 of the body, as serpents, eels, and leeches ; or by varying the form of the body by 

 alternate contractile and expansive movements, as the Medusae. 



1 909. In these dif event displays of voluntary motion, the muscles are only able to 

 continue in exercise for a limited period, during which the irritability diminishes, and 

 the further exertion of their powers becomes painful. When thus fatigued, animals 

 endeavour to place themselves in a condition for resting, and fall into that state of 

 temporary lethargy, denominated sleep. 



1910. The positions assumed by animals during sleep are extremely various. In the 

 horse, they even differ according to circumstances. In the field he lies down, in the 



