75 
THE MAMMALIA— MAN AND BEASTS. 
utider the epidermis, or outer skin of animals. With Plants, this is owing to tho 
inert secretion of tho green matter, or clirmnnh, and its ceasing to colour the cuti- 
c.ular tissues. In all species, softness and moisture are tho results of this albinism or 
whiteness. Its ultimate cause is the want of vital energy, arising either from the 
prolonged abscnco of the inlluence of Light upon the organic structure, or from the 
intensity of a long-continued cold. Its cfiect.s may be either absolute and total, or 
merely partial and local, even among the white varieties of animals and plants. Its 
general tendency is to effeminate all beings. 
Accidental albinism may arise from old age, or the want of a continued renewal of 
this coloured layer, wliieh communicates it.s hue to tho Hair, Feathers, or Scales. 
It may be even induced before old age by disease, or by the absence of the usual 
supplies of nutriment, or, among animals, by the violence of fear or any sudden emo- 
tion, wbie.h may serve to withdraw from the exterior of tiie body its secretions, and 
render tiie skin pale, or the liair white. Tiierc is also an accidental albinism from 
the mechanical injury of tlie raucous pigment, arising from the bruising or tearing of 
the skin, and on these spots, white hair or feathers will arise in tiie place of coloured 
appendages. 
An opposite state of deep blackness, or .IfedciwiV/n, when the surface is said to bo 
mefaiiose or blacky .arises from tlic superabuudauce of tlic mucous subcutaneous tissue 
in aiiimahs atid plants, in which carbon exudes towards the exterior. Sucli are Ne- 
groes, and all black or dark-brown animaks, lurid ami venomous plants, as the Solaneaj. 
This stale of the skin is well fitted for skies, resplendent with Light and Heat. It 
is attended in individuals with dryness, rigidity, and shortness of stature. 
Excessive cold, combined with the absence of Light, serves to drive the nutritive 
and repairing juices far from the skin. This kind of albinism is especially remarked 
in animals inhabiting the liighest mountains and the polar regions, where they become 
white in winter and coloured in summer. The large species of the Porcupine exhi- 
bit these alternate annulatioiis of white and brown, which are due to the alternations 
of summer and winter. A similar effect might be produced on live Sparrows, by pluck- 
ing tho feathers, and rubbing their naked bodies with Spirit-of-wine. The feathers 
which then succeed remain while, because tho alcohol prevents the secretion of the 
colouring subcutaneous matter, in the same manner as an excessive cold. A corre- 
siionding effect may be produced by simibir means upon the Mammalia. 
The colours of animals are intimately ooiiuected with the latitude of the place as 
well as with the changes of the seasons, and seem, in general, delicately sensible to 
the external stimuli of Light and Heat. In Mammalia and Birds, we find fliat the 
hotter regions of the globe, as well as the summer months, are favorable to deep 
and bright colours. 
Sir John Leslie's experiments on colour, as affecting the radiation and absorp- 
tion of Heat, afford the best explanation of tlio final causes of these changes. “ The 
rate at wliieh bodies cool is greatly influenced by their colour. The surface which 
reflects heat most readily suffers it to escape but slowly by radiation. Reflection 
takes place most readily in ulijects of a white colour, and from such, consequently, 
heat will radiate with difficulty. If wo suppose two animals, the one black, and 
the other white, placed in a higher temperature than that of their own body, 
the boat will enter the one lliat is hlaidc with the greatest rapidity, and elevate 
its temperature considerably above the other. Those differences are" observable in 
wearing black and light colour.'d clothes during a hot day. AVhen, on the other 
hand, these animals are jilaccd in a aituation, the temperature of which is consider- 
ably lower than their own, the black animal will give out its heat by radiation to 
every surrounding oiijcct colder than itself, and speedily have its temperature reduced; 
vvliile the white animal will jiart with its heat by radiation at a much slower rate. The 
change of colour in the dress of animals is therefore suited to regulate their tempera- 
ture by the radiation or absorption of caloric. Wliile it is requisite that tiie tem- 
perature of some species should be preserved as equally as possible, tiie cooling effects 
of winter are likewise resisted by an additional quantity of heat being generated in 
the system. An increase in the quantity of clothing takes place, to prevent that 
heat being dissipated by communication with the cold objects around, and tho dress 
changes to a white colour to pi-event its loss by radiation. In summer, the perni- 
cious increase of temperature is prevented by a dlmiuislied seeretion of heat, or the 
■secretion of cold, increased perspinition, the ca^tinff of a portion of tlie winter cover- 
ing, and by a superior intensity of colour in the remainder giving it a greater radlat- 
mg power. The last character would, in the sunshine, by absorbing heat, prove a 
tiuurco of great inconvenienee, were its effects not counterbalanced by other arrange- 
ments, and by the opportunity of frequenting the refreshing shade, or bathing in the 
stream.” Animals become light or gray in old age, and thus the too great dissipa- 
tion of heat in their systems is prevented. 
If it were possible for any one to doubt the fact that the functions of ammaks and 
filants correspond with the movements of tho terrestrial globe, he would find a 
convincing proof in the influence of the seasons, upon the casting of liair among the 
■Mammalia, tlic moulting of Birds, the changes of skin among the lower animals! and 
•ho defoliation of Plants. 
In the .Spring, all Nature is living and vegetating, exiianding and developing its 
I'i'oductions ; the earth is clothed with verdure, tho animals are dressed in their 
nuptial garbs, and their amours commence. The cause of tills external cxiiansion of 
all beings originates in tlie circumstance that their functions, long opiiressed hv the 
cold of winter, have actiuircd a superabundance of juices, sap, .and nourisliinent, 
■"hieh only await the favorable mumeut of external heat to expand. Their germs are 
evelopod with extreme vigour. In the human race, there is at this season a doter- 
•nmatiou towards the skin, erupt ive maladies become more prevalent, and exanthemata 
sometimes ajipear as thougli budding were not exclusively conlim'd to the vegetahlo 
mgdora. 'Jhe Hair, Feathers, Homs, .Scales, and Epidermis of animals, as wcdl as 
>e Leaves, Flowers, and Fruit of vegetables, whicli have grow n and expanded dur- 
the Spring, assume their most glittering hues, if not during Summer, at least 
h( tueiiths of tho year, when in our climate the sun is most above the 
^Tizon. But at the approach of the autumnal equinox, living bodies, whctlier 
mia s or I lants, are exhausted by the excessive action of their vital forces during 
fflmer, and their lunetions become less vigorous, in proportioti as Light and Heat 
diminish witli the enfeebled rays of the Sun. Those c.xtcrnal parts, proi'iic«l in Ih • 
preceding Spring, cease to receive nutriment from the body; tliey have furihei- 
arrived at the full period of their growth, and are incapable of receiving any more. 
Hence they dry up or fade away; others become detached and fall. Sooner or later 
at this season, we invariably witness the casting of hair, feathers, scales, horns, and epi- 
dermis, as well as the dropping of flowers, leaves, and fruit, when each Living Being 
enters into a kind of autumnal concentration prcjiaratory to the rigour of winter. 
In the southern hemisphere, our winter being then its summer, and reciprocally, 
the periods of casting or moulting are in each year opposite to ours. 
In the Torrid Zone, the Sun passes twieo a year from the one tropic to the other, 
so that it produces, to a certain extent, two winters and two summers. The winter 
IS there the season of continual rains ; it also determines twice a year tho casting or 
moulting period of anjinals and plants, and doubles the number of the rutting seasons, 
Fiom these circumstances, it arises that Living Beings experience a two-fold waste 
of vital force, and live in these waimer regions at a faster rate tlian elsewhere. Tliey 
arc continually producing or wasting; new flowers spring up next to the fruit ; new 
leaves replace the oid and faded; the Bird prepares its nest of eggs, and sings new 
cai-ols wilhin the hearing of its brood of six months old ; and the Quadrupeds con- 
sume ill a continual slate of generation, gestation, and lactation. 
In colder countries, and on the summits of elevated mountains, there exists another 
kind of change iu tho feathers of Birds and tho liair of Mammalia, which arrives at 
the period of winter. The white robe, the symbol of chastity and sexual indifference, 
is particularly fitted to these cold regions, in tlie same manner as the brilliant robe 
of summer is in corrospoiidenee with the full vigour and activity of the reproductive 
system. Thus the Hare of the Alps (Leptts turiabitis) and the Ermine, as well ils 
a great number of other Mammalia, witii an immense multitude of Birds of tlie 
Northern Regions, especially the M'aders {Grallm) and tfeb-footed Birds {Palmi- 
pedes), which arc covered in the summer season with hair or feathers of brown ami 
more brilliant hues, acquire a pale gray or uniform white during the winter. 
It has been considered by some, that the white garb of arolie animals serves to 
protect them from their enemies, by assimilating their colour with that of the snow. 
But Nature, pursuing a fair system of leeiprocity, imparts the same colour to the 
beasts and birds of prey, so that, in reality, this provision is less effectual than lias 
been commonly supposed. 
Hr Fleming has made the following observations on the cause of the change of 
colour in those quadrupeds, which, like the Alpine Hare and Ermine, become white 
in winter “ It has been commonly supposed that these Mammalia cast their hair 
twice in the course of tho year ; at harvest, when they part with their summer dress 
and m spring, wlien they throw off their winter fur. 'lids opinion, however, doe! 
not appear to be supported by any direct observations, nor is it coentenanoed by ana 
logical reasoning. If we attend to the mode in which the human hair becomes gray 
as we advance in yeius, it will not be difficult to perceive that the change is not pro 
duced by the growth of new hair of a white colour, hut by a cl.aiige iirUie colour of 
the old hair. Hence there will he found some hairs pale towards the middle, and 
white towards the extremity, while the base is of a dark colour. Now, in ordinarv 
cases, the hair of the human head, unlike that of several of tiie inferior animals,' i's 
always dark at the base, and still continues so during the change to gray ; hence 'we 
arc disposed to conclude from analogy, that the cliange of colour, in those animals 
which become white in winter, is efi'ected, not by a renewal of the hair, hut by a 
change m the colom- of the secretions of the reie-mticosum, by which the hair is 
nourished, or peiliaps by tliat secretion of the colouring matter being diminished or 
totally suspended.” An Ermine shot by Dr Fleming in May 1814, in a garb inter- 
mediate to its summer and winter dross, confirmed this view of the subject. In all 
the under parl.s of its body, the white colour had nearly disappeared, hi exchange for 
the primrose-yellow, the ordinary lingc of these parts in summer. The upper “parts 
had not fully acquired their ordinary summer colour, which is a deep yellowish-brown. 
There were still several white spots, and not a few with a tinge of yellow. Upoii 
examining those white and yellow spots, not a trace of iiitorspersod new .short brown* 
hair could be discerned. This would certainly not have been the ease if the change 
of colour is eflccted by a eliaiige of fur. Besides, while some parts of the fur on the 
back had acquired their proper colour, even in those parts numerous liairs could he 
observed of a wax-yellow, and in all the intermediate stages from yellowish-brown 
tlirough yellow to white. These observations leave little room to doubt that the 
change of colour takes place in the old hair, and that tlie change from white to brown 
passes through yellow. If this conclusion he not admitted, then we must suppose that 
this animal casts its hair at least seven times in the year. In spring it must produce 
Iirinirose-yellow hair, then hair of a ivax-ycllow, and lastly of a yellowish-brown 
The same process must he gone through in autumn, only reversed, and witli the ad 
dition of a suit of white. The absurdity of this siiiipositimi is too apparent to he 
furllier exposeil. Thus the hair, as long as it remains connected with tho body, 
participates in llic general life of tho system, and is influenced in respect to its colom- 
by tho secretions of the mucous net-Mork of the skin. 
There exists a general tendency iu all living bodies to develop themselves 
from within, outwards. 1 Ids evululioii of living bodies is the ultimate cause of tho.so 
changes wliieh the external surface of their bodies undergoes during tlio several pe- 
riods of their existence, and determines the variations in the quantity of their cloth- 
ing : the proximate causes of cliange are the external stimuli of light and heat. As 
each appendage ol the animal body is endowed with a vital power peculiar to itself, it 
must have its peculiar periods of youth, perfection, decay, and death. When anv 
organic portion of tlic body is completely dead, it separates and falls, because a livinir 
suhstaiiee cannot eo-exist with a dead one. 'i'he casting of hair, and all other kinds 
of moulting or external change, is nothing more than tlie natural deatli of a certain 
liortion ol an animal body, in consequence of the development of other parts interior 
to it, and lliis kind of function is regulated by fixed laws. 
The external parts of animals and plants w hith are renewed each year are of two 
kinds. They may liavc a peculiar organic conformation, as we find in hair, liorns 
teeth, leathers, and loaves, or tlii'v may Imve a simple structure, scalv or foliaoeous 
as We find iu the epidermis or outer skin, shells, and memhraucs. 
