FUNCTIONAL INDEPENDENCE OF THE UNITS OF THE BODY.
Page 364.
Physiologists agree that the whole organism consists of a multitude of elemental parts, which are to a great extent independent of one another. Each organ, says Claude Bernard, has its proper life, its autonomy; it can develop and reproduce itself independently of the adjoining tissues. A great German authority, Virchow, asserts still more emphatically that each system consists of an “enormous mass of minute centers of action.... Every element has its own special action, and, even though it derive its stimulus to activity from other parts, yet alone effects the actual performance of duties.... Every single epithelial and muscular fiber-cell leads a sort of parasitical existence in relation to the rest of the body.... Every single bone-corpuscle really possesses conditions of nutrition peculiar to itself.” Each element, as Sir J. Paget remarks, lives its appointed time and then dies, and is replaced after being cast off or absorbed. I presume that no physiologist doubts that, for instance, each bone-corpuscle of the finger differs from the corresponding corpuscle in the corresponding joint of the toe; and there can hardly be a doubt that even those on the corresponding sides of the body differ, though almost identical in nature. This near approach to identity is curiously shown in many diseases in which the same exact points on the right and left sides of the body are similarly affected; thus Sir J. Paget gives a drawing of a diseased pelvis, in which the bone has grown into a most complicated pattern, but “there is not one spot or line on one side which is not represented, as exactly as it would be in a mirror, on the other.”
Many facts support this view of the independent life of each minute element of the body. Virchow insists that a single bone-corpuscle or a single cell in the skin may become diseased. The spur of a cock, after being inserted into the ear of an ox, lived for eight years, and acquired a weight of three hundred and ninety-six grammes (nearly fourteen ounces) and the astonishing length of twenty-four centimetres, or about nine inches; so that the head of the ox appeared to bear three horns. The tail of a pig has been grafted into the middle of its back, and reacquired sensibility. Dr. Ollier inserted a piece of periosteum from the bone of a young dog under the skin of a rabbit, and true bone was developed. A multitude of similar facts could be given.
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Page 368.
What can be more wonderful than that characters, which have disappeared during scores, or hundreds, or even thousands of generations, should suddenly reappear perfectly developed, as in the case of pigeons and fowls, both when purely bred and especially when crossed; or as with the zebrine stripes on dun-colored horses, and other such cases? Many monstrosities come under this same head, as when rudimentary organs are redeveloped, or when an organ which we must believe was possessed by an early progenitor of the species, but of which not even a rudiment is left, suddenly reappears, as with the fifth stamen in some Scrophulariaceæ.
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Page 369.
In every living creature we may feel assured that a host of long-lost characters lie ready to be evolved under proper conditions. How can we make intelligible, and connect with other facts, this wonderful and common capacity of reversion—this power of calling back to life long-lost characters?
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Page 336.
Imperfect nails sometimes appear on the stumps of the amputated fingers of man; and it is an interesting fact that with the snake-like saurians, which present a series with more and more imperfect limbs, the terminations of the phalanges first disappear, “the nails becoming transferred to their proximal remnants, or even to parts which are not phalanges.”
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Page 387.
Mr. Salter and Dr. Maxwell Masters have found pollen within the ovules of the passion-flower and of the rose. Buds may be developed in the most unnatural positions, as on the petal of a flower. Numerous analogous facts could be given.
I do not know how physiologists look at such facts as the foregoing. According to the doctrine of pangenesis, the gemmules of the transposed organs become developed in the wrong place, from uniting with wrong cells or aggregates of cells during their nascent state; and this would follow from a slight modification in their elective affinities.
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Page 388.
On any ordinary view it is unintelligible how changed conditions, whether acting on the embryo, the young or the adult, can cause inherited modifications. It is equally or even more unintelligible, on any ordinary view, how the effects of the long-continued use or disuse of a part, or of changed habits of body or mind, can be inherited. A more perplexing problem can hardly be proposed; but on our view we have only to suppose that certain cells become at last structurally modified, and that these throw off similarly modified gemmules. This may occur at any period of development, and the modification will be inherited at a corresponding period; for the modified gemmules will unite in all ordinary cases with the proper preceding cells, and will consequently be developed at the same period at which the modification first arose. With respect to mental habits or instincts, we are so profoundly ignorant of the relation between the brain and the power of thought that we do not know positively whether a fixed habit induces any change in the nervous system, though this seems highly probable; but, when such habit or other mental attribute, or insanity, is inherited, we must believe that some actual modification is transmitted; and this implies, according to our hypothesis, that gemmules derived from modified nerve-cells are transmitted to the offspring.