Frog leg

“ The blood circulates in the hind leg of a frog for many minutes after the removal of the heart, which meanwhile keeps up an independent motion of its own. Vitality can be so divided in the earthworm, that, as demonstrated by the experiments of Spalanzani, each of the severed parts carries life enough away to set it up as an independent animal ”

“ The under part of the body follows the edge of the lower lap of the envelope from front to hind leg. Now flatten out the fold at the top and bend the paper under at the corners, [48] which forms the head and tail. Cut a slit along the folded edge of the head for the mouth, pull the lower part down and the mouth will open wide as a frog's mouth naturally does. By working the lower jaw the frog can be made to snap at imaginary flies. Draw the eyes as shown in Fig. 87 and bend down the lower part of the body along the dotted line, shown in Fig. ”

“ When quiet, the fore limbs are weak, and the hind legs drawn up very peculiarly, the thighs being jammed up so against the body, that they come to lie on the dorsal aspect of the sides of the frog, and the legs are so much flexed that the feet lie on the animal’s back, quite internal to the plane of the thighs. ”

“ What can be so well adapted for the expansion of the foot, when a portion of the weight of the body is thrown on it? How easily will these irregular surfaces yield and spread out, and how readily return again to their natural state! In this view, therefore, the horny frog is a powerful agent in opening the foot; and the diminution of the substance of the frog, and its elevation above the ground, are both the cause and the consequence of contraction: the cause, as being able no longer powerfully to act in expanding the heels ”

“ If, then, we reduce the frog's nervous system to the spinal cord alone, by making a section behind the base of the skull, between the spinal cord and the medulla oblongata,{93} thereby cutting off the brain from all connection with the rest of the body, the frog will still continue to live, but with a very peculiarly modified activity. It ceases to breathe or swallow; it lies flat on its belly, and does not, like a normal frog, sit up on its forepaws, though its hind-legs are kept, as usual, folded against its body and immediately resume this position if drawn out. ”

“ The feet of the hind legs are webbed and have five fingers or toes.
[Pg 225]
The frog has a backbone, but no ribs. As he is ribless he cannot expand and contract his chest in breathing, so that he must swallow what air he wants. In swallowing air he must close his mouth and take the air in only by the nostrils; therefore, oddly enough, if his mouth is forcibly kept open he may be smothered. [64] The frog’s breathing is partly through its skin, which gives off carbonic acid gas; and moisture is as needful to a frog’s skin as to the gills of a fish. ”

“ She held her broad browed head erect, the bristles pointed like needles from her blood-streaked muzzle, grit and pluck could be traced in her every movement, and, in her eyes, universal defiance.
Down the dark watercourse she went, twisting her lithe chestnut body S-wise in and out of the coarse grass-clumps. A frog leaped before her. In a flash she had flung herself upon it, her white teeth clicked together in its brain, and she sauntered slowly out of sight, bearing her latest victim in her mouth. It was hideous. To eat vegetables was natural enough, but to eat living, quivering flesh! ”

“ Although the frog is essentially a land animal, it is quite at home in the water, and swims gracefully and easily by the help of the webs which connect the long toes of its hind feet. On land, it progresses by long leaps, its limbs and body being [Pg 335] well adapted to this habit. As is usual in leaping animals, the hind legs and feet are markedly longer than the fore limbs; and the shortness of the body enables the two pairs of limbs to be brought together to break the shock of the fall. ”

“ When far advanced, contraction offers signs that cannot well be missed. The converging of the heels narrows the V-shaped indentation in the sole for the reception of the frog. As a consequence of this, the frog itself becomes atrophied by reason of the continual pressure exerted upon it by the ingrowing horn of the wall and the bars. The median and lateral lacunæ of this organ, from being fairly broad and open channels, become pressed into mere crack-like openings (see the commencing of this condition in Fig. 80, and a badly wasted frog in Fig. 74A) . ”

“ If it be true, as is asserted by some observers, that taking off the skin of the legs of the frog (a procedure which causes no pain, as the frog has no consciousness) prevents his shifting himself to maintain his equilibrium when his resting-place is moved, it is plain that the surface-irritations which cause the reflex alterations of position in the brainless frog originate in the skin of the legs and through the sense of touch. There are, however, certain facts which indicate that the impulses under discussion are not of so simple a character. ”

“ Legs, with five digits, are usually present, and are used for swimming, walking, or leaping. The legs are longest and best developed in the short tailless frog and toad forms which are mostly terrestrial, and are short and weak in the tailed salamander forms, many of which are aquatic. The skin is almost always naked, showing a marked difference from the scaled condition of reptiles and most of the fishes, and its cells secrete a slimy, sticky, usually whitish fluid, which in some cases is irritating, or even poisonous. ”

“ Such action is termed “reflex action,” on the supposition that the influence conveyed inwards by nerves going from34 the skin to the spinal cord is reflected back from that cord to the muscles by the other set of nerves without any intervention of sensation. This action of the frog may be carried to a very singular extreme. At the breeding season the male frog tightly grasps the female behind her arms, and to enable him the more securely to maintain his hold, a warty prominence is then developed on the inner side of each of his hands. ”

“ With a frog of good size, low down, and taking part in the pressure of the foot on the ground, contraction will be prevented. On the other hand, an ill-developed frog, one wasted by long-continued and spreading thrush, or one robbed of its normal function by excessive paring in the forge, is a common starting-point of the condition we are considering. ”

“ When the frog, under this circumstance, comes down upon the ground and receives pressure, the pain the animal feels from the ineffectual attempt thus made to expand the inelastic and inflexible heels, causes him to lift the frog a little, and go principally on the toe ”

“ The flat pointed head seems to be in contact with the ground or very near to it as the animal moves about rapidly and erratically. The frog has a proclivity for squeezing into holes and cracks, or beneath objects on the ground. The burst of activity by one that is startled lasts for only a few seconds. ”

“ The point of the frog, much the harder part, extends forward to the centre of the sole. Though situated between the bars the frog is only attached to their upper border—the sides remaining free and separate. Thus on each side is formed a deep fissure which permits the frog to expand laterally when compressed, without such force being continued to the sides of the foot. The frog is elastic, and when pressed upon must expand slightly. ”

“ Does the frog use its fore legs in swimming or jumping? Its hind legs? How is the frog fitted for jumping? Compare it in this respect with a jumping insect; a jumping mammal. How is it fitted for swimming? Is the general build of its body better fitted for swimming or for jumping? How far can a frog jump?
External Features.—The frog may be said to have two regions in its body, the head and the trunk. A neck hardly 130exists, as there is only one vertebra in front of the shoulders (Fig. 252) , while mammals have seven neck (cervical) vertebræ. ”

“ These are known as the Lateral Lacunæ.
The Sides of the frog are flat and slightly oblique. They are closely united to the bars and to the triangular indentation in the posterior border of the sole.
The Base of the frog is formed by the extremities of its branches, which, becoming wider and more convex as they pass backwards, form two rounded, flexible, and elastic masses separated from each other by the median lacuna. ”

“ A big frog from the neighbour pool, unaware that there had been any intrusion here, came swimming up, on some errand of private urgency, and made directly for the log. The next instant, before he had any inkling of the imminence of doom, the raccoon's forepaw shot out like a flash. It was a wide-spread, flexible paw, like a little, black, lean hand, strong and delicate, the fingers tipped with formidable claws. It caught the swimming frog under the belly, swept him from the water, and threw him far up on to the shore. ”

“ Placing the frog on its back, with forceps firmly grasp the skin of the abdomen and the muscles beneath, just in front of the hind legs, and with the scissors cut straight forward in the middle line until the floor of the mouth is reached; this will separate the arms. Care must be taken not to cut too deeply, but this may be avoided by keeping the skin uplifted. ”

“ If he does not turn round and beat the work smooth with his tail, then I require to know for what purpose he carries that broad, heavy, and hard tool behind him.
How few even among lovers of Nature know why a frog has no tail! The reason-is simply that it used that organ up when it was in want. In early life, as a jolly tadpole, it had a flourishing tail to swim with, and gills for breathing water, and an infantile mouth for taking vegetable nourishment. But when it began to draw near to frog's estate, serious changes were required in its structure to fit it for the life of a land animal. ”

“ The skin in this, the typical genus, is smooth; the hinder legs are very long, muscular, and formed for leaping; the toes of the hind feet are connected by a web; there are teeth on the upper jaw, and on the palate; the gape is very wide; the tongue, broad, soft, notched at the extremity, is folded back, the anterior portion lying ordinarily on the posterior; the eyes are brilliant and prominent, and elevated above the forehead.
The Common Frog (Rana temporaria, Linn.) is familiar to every child. ”

“ It is very strong, and often destroys the Spring Frog. It inserts the claws of the two fore-feet into one of the frog's hind legs, and with the claws of its hind feet it grapples rice-stubble, or some aquatic plant; the frog unable to disengage itself becomes exhausted by struggling. ”

“ The flying-lemur is the best furnished in this respect, as it has not only a very extensive "alar membrane," but a short expansion of skin connects together not only the fingers but the toes also (which is not the case in bats) , and has a true interfemoral membrane extending from the hind-legs to the tail.
Fig. 3.—A Flying Frog.
There is no other such instance in beasts, or in any existing reptiles; but web-footedness is carried to such an extreme degree in a certain frog found in Borneo as to give rise to the conjecture that it was a flying animal. ”

“ Thus if I merely remove his hemispheres and tilt my: hand down, he will crawl up it but not jump off. If I pinch him under the arm-pits, he mill croak once for each pinch; if I throw him into water, he will swim until I touch his hands with a stick, when he will immediately stop. Over a frog with an entire brain, the physiologist has no such power. The signal may be given, but ideas, emotions or caprices will be aroused instead of the fatal motor reply, and whether the animal will leap, croak, sink or swim or swell up without moving, is impossible to predict. ”

“ On soft or uneven soil, the entire lower border of the wall, the sole, bars, and frog came into contact with the ground: nature intended them to meet the ground, and there to sustain the animal's weight as well as the force of its impulsive powers. On hard or rocky land with a level surface, only the dense tough crust and bars, the thick portion of sole surrounded by them, and the resilient retentive frog meet the force of the weight and movement; and in both cases, not only with impunity, but with advantage to the interior of the foot, as well as the limb. ”

“ They grow into legs. Then the gills go inside and become lungs. The hind legs come next. The tail grows shorter, and the animal broader. One day the tad-pole is gone. The frog jumps out on a rock and catches an insect for dinner. He sits blinking in the sun as if he wonders how he did it. The frog is a land animal that grew from a water baby. It likes to live on the edge of a pond where it can dive and swim whenever it feels like it. ”

“ The entire frog family is as protectively colored as this least member, the cricket-frog. They all carry fern-seed in their pockets and go invisible. Notice the wood-frog with his tan suit and black cheeks. He is a mere sound as he hops about over the brown leaves. I have had him jump out of the way of my feet and vanish while I stared hard at him. He lands with legs extended, purposely simulating the shape of the ragged, broken leaves, and offers, as the only clue for one's baffled eyes, the moist glisten as his body dissolves against the dead brown of the leaf-carpet. ”

“ It is impossible to watch the horizontal motions of a frog in the water, as it is impelled by these muscles and its webbed feet, without being struck by the complete resemblance in this portion of its frame to human conformation, and the almost perfect identity of the movements of its lower extremities with those of a man making the same efforts in the same situation. ”