Book U. DISTRIBUTION OF ANIMALS. 295 



Chaf. VI. 

 Of the Distribution of Animals, 



1962. The geographical distribution of each species of animal ^ Dr. Fleming observes, 

 may be represented by a circle, towards the centre of which, existence may be comfort- 

 ably maintained ; but as we approach the circumference, restraints multiply, and life at 

 last becomes impracticable. Each species has a range peculiar to itself, so that the circle 

 of different species intersect one another in every possible relation. Hitherto the geo- 

 graphical limits of but few species have been satisfactorily determined. These chiefly 

 belong to the larger species of quadrupeds, as the African and Asiatic elephants, the ass 

 and the quagga, the lion, hippopotamus, and polar bear. In the tribes of the less 

 perfect animals, the species of which have been investigated by few, the extent of their 

 geographical distribution has been very imperfectly determined. They appear to be 

 limited to circumstances connected with temperature, food, situation, and foes. 



1963. The degree of heat at the equatorial regions appears to be most favorable for the 

 increase of living beings, and they diminish ia-numbers as we approach the poles. There 

 is no latitude, however, which tlie perseverance of man has yet reached, where living 

 beings have not been observed. The icy shores of the arctic regions are peopled as well 

 as the arid plains or shaded forests of tropical climates. When, however, an inhabitant 

 of the colder regions is transported to a warmer district, the increased temperature is 

 painful, the functions become deranged, and disease and death ensue. The inhabitants 

 of the warmer regions, when transported to the colder districts, experience inconvenience 

 from the change of temperature, equally hurtful to the system, and fatal to its continu- 

 ance. The polar bear appears to be accommodated to live in a region, whose mean 

 annual temperature is below the freezing point. In those districts where the individuals 

 of a species are most vigorous and prolific, the temperature most suitable for existence 

 prevails. The native country for the horse is probably Arabia. There he exists in a 

 wild state in the greatest numbers. In the Zetland Islands, where he is nearly in a state 

 of nature, he is approaching the polar limits of his distribution. He has become a 

 dwarf. He does not reach maturity until his fourth year, seldom continues in vigor 

 beyond his twelfth, and the female is never pregnant above once in two years. At the 

 line, where the energies of the horse terminate, however, the reindeer becomes a useful 

 substitute. Its equatorial limits do not reach the shores of the Baltic. 



1964. To compensate the variations of the seasons a variety of changes take place in the 

 circumstances of animals. The clothing of animals, Uving in cold countries, is not 

 only different from that of the animals of warm regions in its quantity, but in its ar- 

 rangement. If we examine the covering of swine of warm countries, we find it con- 

 sisting of bristles or hair of the same form and texture ; while the same animals which 

 live in colder districts, possess not only common bristles or strong hair, but a fine friz- 

 zled wool next the skin, over which the long hairs project. Between the swine of the 

 south of England, and Scottish Highlands, such differences may be observed. Similar 

 appearances present themselves among the sheep of warm and cold countries. The 

 fleece of those of England consists entirely of wool ; while the sheep of Zetland and 

 Iceland possess a fleece, containing, besides the wool, a number of long hairs, which 

 give to it, when on the back of the animal, the appearance of being very coarse. By 

 means of this arrangement, in reference to the quantity of clothing, individuals of the 

 same species can maintain life comfortably in climates which differ considerably in 

 their average annual temperature. 



1965. The process of casting the hair takes place at different seasons, according to the 

 constitution of the animal with respect to heat. The mole has, in general, finished this 

 operation before the end of May. The fleece of the sheep, when suffered to fall, is 

 seldom cast before the end of June. In the northern islands of Scotland, where the 

 shears are never used, the inhabitants Avatch the time when the fleece is ready to fall, and 

 pull it off with their fingers. The long hairs, which likewise form a part of the covering, 

 remain for several weeks, as they are not ripe for casting at the same time with the fine 

 wool. 



1966. The moulting of birds is another preparation for winter, which is analogous tb 

 the casting of the hair in quadrupeds. 



1967. The distribution o/" cofor in the animal kingdom, appears to be connected with 

 the latitude as correlative with temperature. In the warmer districts of the earth, the 

 colors of man, quadrupeds, and birds, exhibit greater variety, and are deeper and 

 brighter, than in the natives of colder countries. Among the inhabitants of the tem- 

 perate and cold regions there are many species which, in reference to the color of their 

 dress, do not appear to be influenced by tlie vicissitudes of the seasons. In others, a very 

 marked difference prevails between the color of their summer and winter garb. A few 



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