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Show 360 ACCLIMA'l'ION; OR, TilE INFLUENCE OF when we reach tho tertiary, we find the shell animals approaching nearer, in specific forms, to existing species, than those of previous formations; and along with these arc skeletons of birds and mammalia, including quadl'Upcds and quadrumana. 'l'ho geological epoch of man has yet to be determined: it is certain that the investigations of each su •cccding yoat· tend to throw it further back in time; nor arc thoro wanting good authorities who would not be surprised to find his remains in tho tertiary, whore tho quadrumana have boon recently, and for tho :first time, discovered. A discussion of such difficulty and magnitude as tho theory of progrcr;sivc development, would be out of place here; but this idea seems to have taken poss ssion of many of our leading authoritico. Nor, at fit·st sight, would it seem that the lollg-mootod question of tltc origin of species could properly find a place in an essay Oll Medical Climate; yet all these subjects have points of contact, which render it difficult to isolate them. Our ol~j ct being to study the inflnoncc of climates and their diseases on ?'aces, wo assuredly, a prior·i, shonld expect species and more varieties to be influenced in dill' rent degrees. Natural history teaches us that the white and blacl ~ races, for example, arc distinct species. W o should, therefore, regard their origin as independent of climate; and if we can show that these races arc not afrcctcd in like manner by diseases, we fortify tho onclusion to which natural history has led us. Well-ascertained '7 varieties of a given species, however widely scattered, may exchange habitations with comparative impunity; while, on the contrary, as a general I'Ulo, each species of a genus has its proscribed geographical rano-o. 'l'hc spcoios, for example, of the reindeer and tho white boar, in th Arctic, can no more exchange places with the deer and beat· of the Tropics, than can the Esqui.mau with tho tropical Negro. Such facts as those, then, clearly show bow deeply our subject implicates the inv stigation of species and varieties. A gl'cat diversity of opinion has existed with regard to the orio-in of species, but we shall allude only to two of the more promine0nt. Of the first school, Cuvicr may be regarded as the most distino-uishcd authority. IIo contends that the gcolo()'ical bistory of th~ earth ?bould be divided into distinct periods, each of which is complete in 1tsclf; that there has boon, since the dawn of lifo a succession of distinct creations and destructions; and that tho or~anizcd beings of one pooh have no direct connection, by way of descent, with those of the preceding. According to this theory, tho species of animals and plants now scattered over the face of the earth arc primordial forms, the result of a special creation; which have endured without CLIMATE AND DISEASES ON MAN. 3Gl ma~crial. chango to the p~·cso.nt, and which will endure unchangcJ unttl thou· allotted t rm of cxlstcncc has expired. The opposing scl1ool may be represented by Gcoffi·oy St. IIilai.r', tho contemporary of Cuvicr. It is contended by his followers that there has boon but one creation, and no csr;ation of lifo, since tltc first organized beings were brought into cxit>tcncc; that, by a law of pt'OO'l'Cssivc development or evolution, in accordance with new climatic initucnccs, brought into action, irom time to time, by changes in the physical condition of tho globe, tho living beings of one period have given origin to those which follow; and so on through tho whole chain, from the earliest aud simplest forms to the la t and most complex. Moreover, that what we term species remains pcrman nt as long as the physical conditions which produced them remain nn chang d. Some of this school go so far as to ass l't that no such thing as "species" exists; that N aturc creates only individuals, no two animals or plants being oxa tly alike, and tho species of each genus mnning together so closely as to leave their boundari es cliflicult, and often impossible, to define. They further contcn<l, that tran formations of species arc incessantly going on around uH, th ngh so slowly as not to be easily rccoguizccl, in tho atom of time which has been consumed so far by tho human family. Those who contend that all tho races of men arc of common origin, must, in spite of thcmsol vcs, 1hll into these heterodox opinionH of J_,amar k, Ok n, and St. IIilait·c; because the races of men difll·r quite as much, anatomically and physiologically, as do the species of other genera in the animal ki11gdom- the ]~<]_uid oo , the UrsinC'K, Fclin s, &c. I rofcssor Owen himself cannot point out grcatt:t· diftct· nccs between tho lion, tiger, and panther, or the dog, fox, wolf; and. jackal, than those between the ·white Man, Negro, and Mono-ol. Acco t·ding to the above doctrine, not only arc the individuals of our pt· t>cnt Fauna and Flora direct descendants of tho fossil wodd, but they al'c probably destined to be the ancestry of others st.ill mol'c perf ct. The climatic inltneuccs now at work, it is supposed, will be changed, and development take np its line of march and carry on the great plan· of tho Creator. Thns, man himself is to be tlto progenitor of bcin()'s far more pet-feet than himself; and it mnst be confcssccl that th ro js no small room for improvement. But thoro is no good reason why we should cnt r the lists with these cliAputants, as tho two schools unite at a point which meets all the reqn isitions of out· pr s nt investigation. The term species is, at beAt, but a conventional one, without a fixed definition; and is used by both parties to designate certain groups of forms closely resembling |
