MAMMALIA. 397 



In others, again, they assume diverse degrees of development, more or less 

 elongated, as, for instance, in those which are used for clasping or seizing. 

 They are longer and thinner when destined only to walk or to dig. In 

 some mammals, the thumb is opposed to the other fingers or toes, so that it 

 works with the latter as a pincer. In this case, the feet are called hands. 

 The use of the thumb is sometimes also very much reduced. 

 . Generally, the extremities of the toes terminate by horny bodies, which 

 are called hoofs, when they surround all the toes at once ; nails, when they 

 present themselves as mere plates on the upper surface and extremity of the 

 toes ; and finally claws, when they are compressed, pointed, curved, seldom 

 straight, and inserted above at the extremity of the toes. When the claws 

 approach nearer to the nature of the hoof, they are then called hoof-nails. 

 Sloths and ant-eaters, when at rest, can bend backwards their long claws 

 under the sole of the foot, whilst most of the cats and carnivora retract 

 them into a fold of the skin. The two-hoofed mammals, and the hogs and 

 the allied genera, besides the developed toes which are surrounded by the 

 hoof, have usually two small rudimentary ones, provided with hoofs, which 

 are called posterior hoofs, placed above and posterior to the true hoofs. 

 The males oi Ornithorhynchus and o^ Echidna possess, on the heels of the 

 hind feet, a horny spur. The horny envelope sometimes is wanting to 

 many toes, and this is especially the case for the thumb of a few genera. 

 Sometimes, also, the toes are partly or entirely soldered together, or they 

 are united into a membrane fitted for swimming. This membrane some- 

 times extends beyond the tips of the toes, and sometimes reaches only half 

 their length (semi-palmated feet). The fore feet of Cetacea are in a very 

 rudimentary state, and the hind feet are completely wanting. 



For their protection and their defence, the mammals are provided with 

 teeth, claws, or hoofs, and with antlers or horns. The elephant defends 

 itself not only by means of the tusks, but also with its proboscis ; the skunk 

 discharges at its enemy a fetid fluid, secreted by special anal glands ; 

 others attempt to escape by flight, or by feigned death ; still others have 

 spines, scales, or bony cuirasses, as noeans of defence. The quadrumana, 

 or monkeys, make use of surrounding objects, as stones and sticks, to keep 

 off" their enemies. 



The male lives either with one female alone or with several. The female 

 brings forth young either once only or several times a year; and in the 

 colder regions, this takes place during the warmest season. The female of 

 most genera prepares for its young a soft bed ; those only whose young can 

 see and walk, or swim, immediately after birth, as is the case with the hoofed 

 mammals, the seals and cetacea, &c., do not provide such a litter, nor do 

 those which carry about their young. The young of other mammals are 

 very weak when just born, and are often unable to see before nine or four- 

 teen days. The number of young at a birth varies ; usually less as the 

 animal is greater. The hog, however, constitutes an exception. Dogs, 

 foxes, and cats bring forth three to six at a birth. The young are first 

 suckled by the mother, and as long as she feeds them she displays towards 

 them the warmest affection, exposing herself to every danger in protecting 



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