36 TEXT-BOOK OF ZOOLOGY 



nevertheless sufficiently keen to perceive sounds which are to us in- 

 audible. The ears are accordingly pointed and very movable. The 

 sight, too, is excellent. 



4. The wolf pursues its prey running; in fact, it hunts it. In a 

 single night it can easily accomplish a distance of forty miles. Let us 

 examine what bodily arrangements render the animal capable of such a 

 performance. 



(a) The body (vertebral column) is not nearly as flexible as that 

 of the cat, and, being laterally compressed, offers less resistance to 

 the air. While running swiftly the head is stretched forwards, thus 

 forming, as it were, the point of a wedge. (Any cyclist will tell us that 

 the air offers great resistance to a swiftly-moving body. When riding 

 fast, especially if against the wind, the rider bends his body forwards, so 

 as to offer the smallest possible surface to the air.) 



(b) Only its toes touch the ground in walking or running. Animals 

 which walk on their toeB, however (Digitigrades), are lighter-footed and 

 swifter than those which walk on their soles (Plantigrades). The former 

 raise their feet from the ground with ease, whereas the latter roll them, 

 as it were, from the heels to the toes. 



(c) The legs are long, only slightly capable of lateral motion (their 

 joints being less movable than those of the cat), and but little bent; 

 hence they are well adapted to swift running. (The feet of the wolf, 

 accordingly, are of no use for creeping, climbing, seizing and killing of 

 the prey, but are only useful for keeping a tight hold of the prey while it 

 is being consumed. 



(d) By means of its short, blunt, non-retractile claws and the thick 

 pads on its toes it is able to plant itself firmly against any unevennesses 

 of the surface. 



(e) Every powerful movement has the effect of raising the body-heat 

 of an animal. Accordingly, there is a considerable rise of the body- 

 temperature of the wolf during a swift run. A rise of the body-tempera- 

 ture, if at all prolonged, is, however, injurious to an animal, especially a 

 mammal, so that it is necessary that the temperature should be speedily 

 brought back to the normal. This is generally effected by the secretion of 

 sweat, in the evaporation of which any excess of heat is withdrawn from 

 the body. But since the skin of the wolf (as well as of the dog) possesses 

 no sweat-glands, this reduction of heat must be brought about by other 

 means. The " panting " of a dog, who is nothing more than a de- 

 scendant of wolf or jackal (see p. 38), when running fast, is a matter 

 of common observation. It is not noticeable to anything like this extent 

 in other mammals under similar conditions, e.g., a fast-running horse. 

 Whereas a dog, while resting or running slowly, only takes from twenty 



