THE LITE OE ANIMALS. 



mean the flat, curved bones attached in the back to 

 the dorsal or thoracic vertebrre, and in front to the 

 sternum or breast-bone and enclosing the chest 

 cavity. The number of the true ribs reaching the 

 sternum and of the false ones, which are either at- 

 tached to it by cartilage or are not joined to the 

 breast-bone at all, is subject to a great many varia- 

 tions. In the skeletons of the Mammals there is 

 great diversity in the structure of the limbs, and in 

 some Whales the hinder pair is totally lacking or 

 the bony skeleton of the animal only reveals two 

 stunted rudiments. In the fore-limbs the shoulders 

 and the hand show the greatest variety; the clavicle 

 (or collar-bone) may be very strong or it may be 

 lacking; the fingers and toes may be all there, or 

 may be stunted, according as the hands and feet 

 become paws, hoofs or fins; the usual number of the 

 fingers — five — may decrease to one. The bones of 

 the leg are also variously developed. 



"The bones of the skeleton are set in motion by 

 muscles, which in some animals are for us the most 

 important part, as they form our daily food. These 

 muscles, which in plain, every-day speech, we call 

 "flesh," are attached to the bones and move them in 

 different directions. It may be sufficient to say 

 that the muscles are developed to a close accord- 

 ance with the skeleton of the animal and the mode 

 of life, which latter is closely allied to its form and 

 general structure. 



"The organs of digestion are very similar, yet 

 they show some variations in their structure. The 

 mouth is always furnished with soft, fleshy lips, 

 plentifully supplied with nerves; the teeth reach 

 their highest development in the Mammals, and are 

 of great importance to the mode of life of the ani- 

 mal, and of special importance to naturalists in its 

 scientific classification. 



"The mouth is connected with the oesophagus (or 

 gullet), which never shows such a dilatation as in 

 birds. The stomach is always more or less thin- 

 skinned, and may be plain or show as many as three 

 compartments. Its arrangement is quite peculiar 

 in those animals which, when time permits, com- 

 fortably ruminate their food and then send it to the 

 digestive organs past the first storage receptacle. 



"The chest cavity is completely closed by the 

 diaphragm; the lungs float in it and do not com- 

 municate with any special pneumatic cavities. The 

 trachea, or windpipe, usually divides into two 

 branches, and has only one larynx, which lies at the 

 upper end of the windpipe and is formed by a vary- 

 ing number of cartilages. A few Mammals have 

 peculiar cavities connected with the larynx, but the 

 vocal chords are lacking only in the Whales. 



"The brain and nerves are variously developed. 

 The former always fills its cavity in the skull, but 

 this cavity may be very small, and the amount of 

 brain is then accordingly slight. In no other Mam- 

 mal does the brain so greatly exceed the spinal cord 

 in bulk and weight as in Man, and in no other ani- 

 mal is the cerebrum (or the higher and front portion 

 of the brain) so developed. This alone shows the 

 structural superiority of Man to all other animals. 

 The organs of sense are similar in all Mammals, the 

 Whale alone showing a marked deviation from the 

 general rule, for although it possesses a nose its 

 sense of smell is certainly very deficient. The 

 organs of hearing are usually perfect, and the ear 

 shows three labyrinths. The sense of vision is not, 

 in Mammals, so greatly superior to the other senses 

 as is the case with birds; the eyes are always two in 



number, usually small in size and never inwardly 

 movable, as with the birds. The sense of taste is 

 acute in Mammals, as may be concluded from the 

 muscular tongue well supplied with nerves. The 

 sense of touch is highly developed and may have its 

 seat in the nose, in the hands or in hairs on the lips. 

 Nearly all parts of the body are sensitive. 



"As a bodily covering hair prevails; yet the coat 

 may consist of scales, bristles, horny shields, horny 

 callosities or simply the skin, which in such cases 

 may have its outer layer developed so as to furnish 

 the requisite protection. The nails may be flat and 

 thin, round and thick, straight or curved, blunt or 

 sharp, and may be nails proper or developed into 

 claws or hoofs." 



The variety in the life of the Mammals is very 

 great, although with most species eating and sleep- 

 ing comprise the daily history of their lives. Yet 

 the lively Monkeys in Africa, the still more odd 

 swinging, prehensile-tailed Monkeys of South Amer- 

 ica, the flitting Bats, the night-prowling beasts of 

 prey, the diving Seals, the leaping Squirrels, the noble 

 Horse, fleet Antelope and other animals lead lives 

 which are peculiarly their own, differing greatly 

 from those of other creatures and affording a most 

 interesting subject of observation. As a rule all the 

 senses, except that of sight, (in which the birds 

 excel) are more completely developed in the Mam- 

 mals than in any other class of animals. The vocal 

 expression of mammals is sometimes remarkable for 

 its volume but very seldom for its beauty, that of 

 Man alone being really musical and superior to 

 the voice of birds. The sounds made by different 

 animals are quite varied, as is illustrated by a com- 

 parison between the mewing of Cats, the barking of 

 Dogs, the lowing of Oxen and braying of Asses 

 with the dismal howls of the Jackal and Coyote and 

 the deafening noises of the Howler Monkeys. 



The varied uses to which the tail is put forms an 

 interesting subject of observation. In Man, the 

 Man-shaped Apes and some varieties of the Sloth, 

 the coccyx, or vertebra? forming the rudimentary tail, 

 curves forward and does not project externally. In 

 the other Mammals it varies from an invisible stump 

 to a most extensive adornment. By most long- 

 tailed animals, the member is used as a weapon of 

 defense against winged tormentors, and Cattle, 

 which are especially subject to annoyance from 

 Flies and Gnats, have a tail which is tufted at the 

 end in such a manner as to afford an effective brush 

 with which to fight these insects. Many South 

 American Monkeys, some of the Marsupials, and 

 other animals, have prehensile tails by means of 

 which they can sustain their entire weight. To the 

 Bats, and also to the Mammals having a membra- 

 nous formation which enables them to flutter through 

 the air, such as the Taguan, the Assapan and some 

 of the pouched animals, the tail serves as a rudder 

 to steer its wearer while progressing through the air. 

 Others have the tail so developed as to use it as an 

 organ of touch, while the Kangaroo utilizes its tail as 

 a third leg, which forms, with the others, a tripod 

 upon which it supports its body when at rest. 

 Some tails, like those of Rats, are nearly or quite bare 

 of hair and are covered with scales, some have a 

 covering of short hair, others are bushy. Some 

 bushy tails, like those of the Squirrel, are what is 

 called distichous, that is, they are arranged or parted 

 into two rows of long hairs and make a pretty or- 

 nament, while the tail of the Great Ant-cater is 

 draped into a long mane. 



