selves to elianged environment is not possessed
to the same degree l>y dilFerent species of one
genus or by the individuals of any species. It
varies with tile hardiliood, with the capacity for
ri'sistame, Imth of tin- individual and of the spe-
cies. Just what the changes are, whether chem-
ical or physical, that go on in the protoplasm
of the body during the period of acclimatization,
we do not. in many cases, know. In the acclima-
tization of fishes to denser media it is apparent
that some solids are taken into the body, for the
fishes sink when transferred again to fresh wa-
ter. Some organisms possess a remarkably high
degree of acclimatization. Thus, few animals
can resist a temperature of over 115° F.. while
105° F. is the death-point of whole groups.
Yet certain organisms live in hot springs in
water of much higher temperature, although
they may be similar in kind to, or even identical
with, those that live in cooler waters outside,
and probably were acclimated to the high tem-
perature by slow degrees as they made their
way up the outlets into the springs. We know
from experimentation that organisms can resist
an amount of heat, of .lensity or of poison
when acoistomed to it by slow degrees, that
would have been fatal ha<i they been subjected
to it suddenly. We owe the fact that certain
doniestii- animals, such as the horse, cattle,
clog, cat, fowls, rats, and mice, have spread
with mankind over nearly all the world to
the great capacity for acclitnatlzatiou of these
forms, most of which have originated in warm
climates. Likewise the ubiquity of such food-
plants as the potato and cereals, as well as cer-
tain weeds, is due to their great capacity of adap-
tation; for those plants and animals that have a
limited amount of adaptation have likewise a
limited range of distribution. The quality and the
strength of some animals seem actually to itn-
prove in a new clifiiate. Thus the merino sheep
imported into Silesia and Pomerania from Spain
seem to be superior iti those lands to their Span-
ish ancestors, while the fleece of the Syrian sheep
becomes finer in Spain ; but in such cases it is
difficult to say just how much is due to climate
and how much to the breeder's skill and care.
Many of our domestic animals have been so long
in the countries in which we now find them that
we can never hope to know anything about the
history of their importations; but the silkworm
is comparatively so Intc an imixirtation into
Kurope that we can follow its progress. It was
brought froui China first into Italy, and now it
is acclimated not only to southern France but
even to the coast of the Baltic Sea. and it is
able to live in some parts of the United States.
Of late years numerous acclimatization socie- ties have been formed (the best known of which is the Soci^'t<' d'.Acclim:itation of Paris), having as their object the transference of seemingly desirable animals from their native lands to other parts of the world where they may thrive to human advantage. This has been found feasible in many instances, so far as the ability to become acclimated is concerned, but in many cases the expected benefits have turned to evils through overnuiltiplication or other means of becoming a local pest, and such experiments are now rarely attempted. The introduction of sal- monoid fishes from the Pacific to the Atlantic side of the I'nited States, and from Euro|)e to New Zealand, of bumble-bees into Xew Zealand, and of several insects, such as ladybirds, as enemies of agricultural pests, are instances of the more benefuial sort. The European house-spar- row in North America, the muugoos and agua- toad in the West Indies, the rabbit in Australia, and a great host of more or less .iccidentally introduced insects destructive of plants, etc., are cases of an opposite character. For particulars in respect to these, see accounts of the respective animals.
In People. This treats of the ability of men to maintain themselves in a country with radically different climatic conditions from those from which they migrate. At present the inevitable teudeniy of European and .American jieoples to spread over the major i)art of the earth gives the question many practical bearings. Can a race and a civilization from the temperate zone be transplanted to the tropics? The question is a double one: (1) Can individuals from the tem- perate zone live in the tropics for a few years and maintain their health and vigor; (2) can they work at their usual occupations, maintain their customary vigor, energy, and ability, rear families and prop;igate their kind for several generations? On the first point most authorities agree in the allirmative, provided reasonable provision for sanitation is made, and temperance and thrift prevail among such emigiants. On the second point authorities differ, with the bal- ance in the negative. Races differ in their abil- ity to adjust themselves to new climatic condi- tions. The individual or the race may not suc- cumb at once when transferred to a very differ- ent climati", and yet the acclimatization may be only partial. Certain organs only of the body may be affected by the changes, so that "diseases of acclimatization" may be induced. Tlius Euro- peans are liable in tropical countries to suffer from diseases of the liver, while natives of the tropics are subjected to pulmonary troubles in temperate zones. The African in the United States has a high death rate from lung affections. On the other hand, loss of hardihood induced by climate may express itself mainly in deteriora- tion in size, as is the case with the Shetland pony. So far as the human races are concerned there seems to be a direct ratio between intelli- gence and capacity for acclimatization. The An- glo-German race is able to endure climatic changes with less loss of vigor than any other European race, and for this reason has been able to surpass all the others as colonizers. High moral qualities are needed. . Homesick- ness is a frequent cause of failure. Temperance and thrift are excellent qualities for success, as evidenced in the history of Jewish and Chinese emigration. Mankind is tolerant of great ex- tremes of climate. — 07° F. to 154° F. being the greatest extremes recorded as having been en- ditred by human beings, though no such range of variation has ever been endured by one peo- ple or in any one place. Xot only temperature but also meteorological conditions have an ef- fect, and moisture is. next to temperature, the most important element.
Bini.ioGRAPTiv. The best general treatment of acclimatization may be found in .1. Hann, Iland- buch dcr Klimnfnlogic (Stuttgart. 1807) ; Dar- win, Thi! Variationn of Animals and Plants Un- der Domcfiticiitioii, revised edition (London, iS75) ; Pavillard. I'li'iiiriits dc bioloijie vrgi'tale (Paris, 1001): .'^chimper, P/laitzctiricogrtii>hie (iuf physiologischrr (Inindlayc (.Jena, 1808) ; HoUick, "Relation Between Forestry and Geology
