Feb. 5, 1 8 74 J 



NATURE 



265 



moutVi is filled with air through the nostrils and kept shut 

 while the internal openings of the nostrils are stopped 

 by the tongue, and the entrance to the gullet is closed. 

 Then, by the contraction of the muscles attached to it, 

 the os-hyoides is elevated ; and every other exit from the 

 mouth being closed, except that leading to the larynx, air 

 is thus driven down the glottis into the lungs. 



Thus for pulmonary respiration it is necessary to the 

 frog to keep the mouth shut ; and in this way, but for the 

 action of the skin, the animal might be choked by keeping 

 its mouth open. 



It has been already stated that the typical segmenta- 

 tion of the limbs is wanting in all fishes, but present in 

 all Batrachians that have limbs at all. Similarly in all 

 Batrachians that have limbs at all the muscles of those 

 limbs have essentially and fundamentally the same ar- 

 rangement as in higher animals. In the higher animals, 

 as in man, the muscles of the limbs belong to different 

 categories named from the kinds of motion to which their 

 contractions give rise. 



Thus, when two bones are united by a moveable joint 

 (as the thigh-bone and shin-bone) muscles which, by their 

 contraction, tend to make the angle formed by such bones 



J. 65. — Deep muscles of cxor surface of Frog's hind foot. (The numbers 

 indicate the digits to which the muscles belong. — No. 1 indicating the 

 first digit or great toe), ab, abductors : ad, adductor ; fb, flexor brevis ; 



,//, fle.\ores profurdi ; /ph, flexorcs phalangium ; op, i_opponens mus- 

 ; muscles. 



acute are termed "flexors." Those, on the contrary, which 

 tend to open out such an angle are termed "extensors." 



In the forearm of man, and allied animals, there are 

 muscles which tend by their contraction to place the hand 

 in a position either oi pronation or of supination. 



When the arm and hand hang down, the palm being 

 directed forwards, the position is that of supination, and 

 the bones of the forearm are situate side by side. 



When the arm and hand hang down, but the back 

 of the hand is turned forwards, the position is that of 

 pronation, and the radius crosses over the ulna. When 

 we rest on the hands and knees, with the palms to the 

 ground, the forearms are in pronation. 



Muscles which tend to place the forearm and hanl in 

 the position of pronation are termed pronators : those 

 which, by their contraction, tend to render it supine are 

 called snpinalors. 



It is somewhat surprising to find in an animal so nearly 

 related to fishes as Menobronchus definite flexors, ex- 

 tensors, pro- and supi-nators essentially like those of 



higher animals ; and these distinctions once established ' 

 persist up to man himself with increasing complications. 



The muscular conformity between the highest and 

 lowest of typically-limbed vertebrates is strikingly shown 

 by the structure of the thigh and leg, the leading muscles 

 of these parts in the frog being so like those of man that 

 the practice of calling them by the same name is abun- 

 dantly justified. 



The perfection of man's hand has been justly the theme 

 of panegyric, esteemed as widely as it is known. The 

 delicacy and multiplicity of the motions of which it is 

 capable are of course greatly due to the number and ar- 

 rangement of the muscles with which it is provided. 



One of the most important of these motions is that of 

 the thumb as placed in opposition to the fingers, and 

 effected by a muscle termed opponcns pollicis. 



An "opponens" muscle is one which passes from the 

 bones of the wrist to one or other of the bones of the 

 middle of the hand called metacarpals, and the opponcns 

 pollicis passes of course, as its name implies, to the meta- 

 carpal of the pollex or thumb. 



No other finger of man's hand is furnished with such a 

 muscle except tl^c little finger, which possesses an op- 

 poncns minimi digiti, passing from the wrist to the fifth 

 metacarpal. The same condition obtains in the apes, 

 though in them the opponens of the thumb is smaller 

 and weaker than in man. Though the foot of man is 

 furnished with many muscles, like the hand, yet not one 

 of the toes is provided with an "opponens" or muscle, 

 passing from the bones of the ankle to one or other of the 

 bones of the middle of the foot, which latter are called 

 metatarsals. The same is the case with the apes, except 

 that the Orang-utan has a small " opponens " attached 

 to the great toe. 



This being premised, the foot of the Frog may well ex- 

 cite surprise as to its rich muscular structure. In addi- 

 tion to very numerous other muscles on both surfaces 

 every one of the toes is provided with a separate op- 

 ponens muscle, each having a muscle which passes from 

 the bones of the ankle to its middle foot bone or meta- 

 tarsal. 



The question naturally occurs on beholding this prodi- 

 gality of muscles — What special purpose is served by 

 the Frog's foot ? Surely mere jumping and swimming 

 cannot require so elaborate an apparatus. 



In fact, however, the Frog does make use of his feet 

 for a purpose requiring actions no less de.xterous and 

 delicate than nest-building. 



In 1S72 Dr. Glinther observed a Frog busily occupied, 

 and industriously moving its hind legs in a singular man- 

 ner. On approaching closely he found it had constructed 

 for itself a shelter in the shape of a little bower, con- 

 structed of dexterously interwoven blades of grass. The 

 circumstances have been kindly transmitted to the author 

 by the obser\'er, in a private letter, as follows : — 



"The 'nest-building' Frog was a large example of 

 Rana temporaria, or csculcnta (I forget which), which I 

 had brought into the garden behind my house. It had 

 taken up its abode in grass, near the edge of a tank, from 

 which the turf sloped abruptly to the level of the garden. 

 When I first disturbed the Frog from its lair, I found that 

 it had lain in a kind of nest, which I cannot better de- 

 scribe than by comparing it to the form of a hare, with 

 the grass on the edges so arranged that it formed a sort 

 of roof over it. Sometimes the animal returned to it, 

 sometimes it prepared a new form close to the old one, 

 which lemained visible for several days until it was 

 obliterated by the growing grass. _^ 



" When in its nest, nothing could be seen of the f'rog 

 but the head. 



" One day I poked the Frog out of its lair ; after two or 

 three jumps it returned to the old spot, and, squatting 

 down on the grass, by some rapid movements of the 

 hind legs it gathered the grass nearest to it, pressing it to 



