The daily morning journal and courier., 1904-01-07
COLOR CHANGE IN ANIMALS.
Theories Concerning the Whitening 1T
 Winter

Theories Concerning the Whitening in
 Winter.
 The winter whitening of animals, though of intense interest to zoologists, is very imperfectly understood Most writers are satisfied to believe that this color change was perfected somehow under the action of natural selection for the protective purposes of adaptation to environment. Its origin they leave as an unsolved problem.
 l I find, however, that the change has a deep physiological significance. There l is. for instance, in mammals definite sequence in which the various parts of the body whiten. This sequence corres- ponds to the summer accumulation of i fat in the panniculus adiposus. Thus the belly. where pempheral fat is thick est, is permanently white, and the rump, where also fat accumulates thick ly, is usually the first part to whiten in winter
 l Many northern mammals and birds not usually regarded as of the winter whitening category are lighter in win lter than in summer. The whiteness or white patches assumed in the former season correspond to the fat tracts, so that these species may be regarded as subject to the same process.
 Tn the northern summer most animals accumulate fat, always in a definite manner as regards the regions where it 1 is deposited. This fat is indicative of de- l ficient oxidization and of sluggish met abolism, and the process of it's aceumu- lation and atrophy are most marked in autumn, at which season metabolism is therefore lowest With the onset of winter cold the atrophy may extend to the hairs. Their pigment Gas observed 1 by Metchnikoff) is then removed, all ways, however, commencing with those parts where peripheral fat is thickest and atrophy, therefore, greatest. Should there be change of coat at this time the new hairs are influenced by the same conditions. Tn very cold Icountries they come up white all over the animal: in more temperate regions the parts only where fat is thickest are white.
 I Although @ pigmented hair can thus undergo atrophy and loss of pigment, I know of no case where the color is re- placed. Animals once whitened remain so until the spring moult.
 These facts apply broadly to birds 1- t.r1f i, are the species which have studied es- lpecially.
 Similar laws govern great deal of the distribution of the white color throughout the vertebrate phylum. wherein the connection between white color and the peripheral fat tracts (thus Indicating local atrophy) may be widely traced. Thus domestic animals, nearly all of which are prized most for their power of accommodating fat, exhibit q strong tendency to the development of white patches. Tn both these and in wild animals the belly, where occurs the principal fat tract, is the most fre- jquently white part; next follow the trump and parts of the neck, of the limbs and of the head.
 Marked exceptions are no doubt fre- quently due to unusual arrangements lof the panniculus adiposus. Thus in the hadger, a representative of a family in which the back is usually winter than the belly, I find correspondingly ex- lceptional arrangement of the fat tracts.
 The white of the head--the .sblaze' of horses, the facial stripes of the badger -often affects regions not of fat accu- Imulation, but where the skin immedi- lately overlies bone and membrane from tals and nasals and zygomatic arch) which thus seem to produce an atrophy Isimilar to that caused by underlying fat
 In many animals the hair atrophy as- sumes the form not of whitening. but of badness. Marine mammals are hair- less in proportion to the development ot their peripheral fat layer fattening cat tie lose their hair, while the badness of man corresponds in position to the
 blaze" of horses, and the bare but tocks of monkeys to the white rumps ot other animals.
 Yellow and red frequently follow the same rules of distribution as white They are well known to be fat pigments
 I must carefully guard myself against
 the extension of my theory to all cases where white occurs in vertebrates. Il lis obvious that not all animals are sub fleet to this atrophy, and that there , must be other causes for absence ot pigment. It seems highly probable , from what I have written that the known unevenness of animal celebration !, is but theexternal indication of unever nutrition in different regions of tht
 body.-Captain Barrett Hamilton ill Ma. lture.