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Reviews and Notices of Books

The Variation of Animals and Plants under Domestication. By CHARLES DARWIN, M.A., F.R.S., &c. Two volumes. London: John Murray, Albemarle-street. 1868.

THERE can be no doubt about the reputation which the author of this work has achieved as a naturalist, whatever misgiving there may be as to the truth of his hypothesis of natural selection. Mr. Darwin is a consummate observer. It is Carlyle, we believe, who says that genius consists of immense painstaking first of all, and in another place remarks that nature looked very differently to Newton and to Newton's dog. The reader of these volumes cannot fail to be struck with the sagacity, delicacy, and penetration of the author's observations. The richness and variety of the information render the book embarrassing to a critic. The author touches on a great number of questions which are of peculiar interest to us in their bearing on biology and physiology, and the etiology of disease.

It is only by taking a very wide and extended view of nature, and by gathering up all the facts and reducing them to a system, that true progress in philosophy is made. In the science of medicine and its allies the laws are often very fragmentary, subsidiary, and confined in the limits of their application; and it is in consequence of the breadth of view and spirit of these volumes that we think them peculiarly suited to medical readers.

There is no occasion to discuss the whole question which is now being fought out by some of the ablest intellects of the age. In reference to the Darwinian hypothesis, these are ranging themselves on the two sides; and it is in a great measure owing to the skill and dexterity with which the host of little facts are marshaled, and the force with which they are made to tell in combination, that the number of those who are giving in their adherence to this view is increasing.

It is only necessary to read the introductory chapter carefully to get at the object the author has in view. In pointing out the wonderful fertility of organic beings the author affords a fair idea of his hypothesis:—

"It has been truly said that all nature is at war: the strongest ultimately prevail, the weakest fail; and we well know that myriads of forms have disappeared from the face of the earth. If, then, organic beings in a state of nature vary even in a slight degree, owing to changes in the surrounding conditions, of which we have abundant geological evidence, or from any other causes; if, in the long course of ages, inheritable variations ever arise in any way advantageous to any being under its excessively complex and changing relations of life—and it would be a strange fact if beneficial variations did never arise, seeing how many have arisen which man has taken advantage of for his own profit or pleasure; if, then, these contingencies ever occur, and I do not see how the probability of their occurrence can be doubted, then the severe and often-recurrent struggle for existence will determine that those variations, however slight, which are favourable, shall be preserved or selected, and those which are unfavourable shall be destroyed."

It has always been felt that one of the strongest points in this hypothesis is that it affords some explanation of and gives a meaning to the correlation of structures, and the homologies underlying their seeming diversities, which none other does:—

"How inexplicable is the similar pattern of the hand of a man, the foot of a dog, the wing of a bat, the flipper of a seal, on the doctrine of independent acts of creation! How simply explained on the principle of the natural selection of successive slight variations in the diverging descendants from a single progenitor! So it is, if we look to the structure of an individual animal or plant, where we see the fore and hind limbs, the skull and vertebræ, the jaws and legs of a crab, the petals, stamens, and pistils of a flower, built on the same type or pattern. During the many changes to which in the course of time all organic beings have been subjected, certain organs or parts have occasionally become at first of little use, and ultimately superfluous; and the retention of such parts in a rudimentary and utterly useless condition can, on the descent theory, be simply understood. On the principle of modifications being inherited at the same age in the child at which each successive variation first appeared in the parents, we shall see why rudimentary parts and organs are generally well developed in the individual at a very early age. On the same principle of inheritance at corresponding ages, and on the principle of variations not generally supervening at a very early period of embryonic growth (and both these principles can be shown to be probable from direct evidence), that most wonderful fact in the whole round of natural history—namely, the similarity of members of the same great class in their embryonic condition—the embryo, for instance, of a mammal, bird, reptile, and fish being barely distinguishable—becomes simply intelligible."

In speaking of the modifying effects of climate on dogs, the author alludes to the fact that several of our English breeds cannot live in India, and that in a few generations they degenerate not only in their mental faculties, but in form. On the authority of Captain Williamson, who has carefully attended to this subject, it would appear that hounds are the most rapid in their decline; greyhounds and pointers also rapidly decline; but spaniels, after eight or nine generations, and without a cross from Europe, are as good as their ancestors.

An Indian army friend told us that a litter of puppies belonging to him all died, and on a post-mortem examination he found the livers of all of them enlarged and diseased. There is but little doubt that a tropical climate is very inimical to the European constitution during the active periods of growth and development, as the amount of mortality among the children of Europeans sufficiently proves.

Mr. Darwin thinks all the domestic breeds of rabbits are the unquestionable descendants of the common wild species. He adverts to the marvellous success in rearing hybrids between the hare and rabbit as a possible cause of the modifications seen in some of the larger races of rabbits that are coloured like the hare; but the chief differences in the skeletons of the several domestic breeds cannot, he shows, have been derived from a cross with the hare.

It is needless to say that on the subject of domestic pigeons our author is very full. Although we do not in the least know the origin of the common tumbler, we may suppose, he thinks, that a bird was born with some affection of the brain, leading it to make somersaults in the air; and he supports this hypothesis by what we know about pigeons in India before 1600, where those remarkable for their diversified manner of flight were much valued, and by the order of the Emperor Akber Khan were sedulously trained and carefully watched.

It is the second volume of Mr. Darwin's work, however, that will be found most interesting to medical readers, and we propose to discuss that in a second article.

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Reviews and Notices of Books

The Variation of Animals and Plants under Domestication. By CHARLES DARWIN, M.A., F.R.S., &c. Two volumes. London: John Murray, Albemarle-street. 1868.

(SECOND NOTICE.)

PROPOSITIONS put before the scientific world have to be weighed and judged entirely on their own merits. The question for as to consider is the truth or falsity of the views set forth; their power or their inadequacy to explain the large number of facts which they embrace, and of which they profess to be the exponent; and whether or not there be any one fact which is so opposed as to be utterly irreconcileable.

Much has been said as to the religious aspect of such books as Mr. Darwin's, and we doubt not that some people have been deterred from making an impartial and candid examination of the author's arguments on this account. Nothing can be more suicidal to the interests and progress of religion than the condition of mind which this betokens. It implies a lack or a pervension of faith not to hold securely to a belief in the power of the truth to protect itself. Quite apart from its doctrines, however, the book is as interesting almost as a novel. Whether all the separate species of animals and plants be the result of as many separate and distinct exercises of the creative fiat, or whether there be a continuity of force extending through the whole chain of organic matter,—these are questions which certainly come within the domain of scientific inquiry.

We ought to consider, with a delightful old writer, that "the wisdom of God receives small honour from those vulgar heads that rudely stare about, and with a gross rusticity admire his works; those highly magnifying him whose judicious inquiry into his acts, and deliberate research into his creatures, return the duty of a devout and learned admiration." We have said thus much because we think that no man can avoid perceiving that it is in nature and art alike: there is no series of abrupt starts and disjointed displays of power, but in place of these a gradual unfolding and development from the simple to the complex. Mr. Darwin's hypothesis has been so looked at and criticised from every possible point of view that it is impossible to say anything new about it. That it, or any other view, comprehends and explains all the facts in the organic world we are far from believing; but we think it may be safely said to be the most successful and philosophical attempt yet made to do so. Some of the arguments urged against it seem to us to have the contrary tendency; as, for instance, that as to the speedy degradation to the natural type of domesticated animals when allowed to run wild. Given certain conditions of life tending to a certain result, these will, with every show of probability, produce that result in process of time; but of course, if those conditions be artificially originated and imposed as by domestication, no sooner are these abrogated than the force of other and natural conditions come into play. That marvellous structural changes may be induced by the operation of a changed condition of life in a short period is proved by a large number of facts, and perhaps by none more clearly than in the case of guinea-pigs. Von Baer declares that guinea-pigs were unknown in Europe before the discovery of America; and now the guinea-pig, as we know it, is only found in Europe, and differs from its American derivative in the most extraordinary way—in colour, habits, endurance of cold, and in fertility (it is three times more fertile than the American); and lastly, between the two animals there is the generic difference that they will not pair together.

But of the arguments adverse to the Darwinian hypothesis there are mainly two of unquestionable cogency and force. The first is the absence of animals and plants during the past ages of the earth possessing the intermediate and transitional forms which we should expect to discover; and this Mr. Darwin answers by an appeal to the insufficiency of our geological record and the slight varieties and unstable nature of the characters which marked those forms. The other difficulty we agree with Prof. Huxley in thinking the most important—namely, the phenomena of hybridism. In order to place as views beyond assault, Mr. Darwin ought to be able to demonstrate the possibility of developing from a particular stock, by selective breeding, two forms (says Mr. Huxley) which should either be unable to cross one with another, or whose crossbred offspring should be infertile with one another. At present, all we can say is, it has not been proved that this cannot be done, although no one has succeeded in effecting it. The reader may consult with advantage the Duke of Argyll's book on "The Reign of Law," and an article in the Quarterly Journal of Science for October last on "Creation by Law," by Mr. Wallace. Able as the Duke of Argyll's volume undoubtedly is (and parenthetically we may add, his description of the mechanism of flight in birds would do credit to say professor of anatomy or physiology), still we think he has not fully grasped Mr. Darwin's arguments.

But it is time that we proceeded to examine Mr. Darwin's second volume. In discussing the wonderful nature of inheritance he has drawn largely upon the labours of physiologists and medical men.

"When we reflect that certain extraordinary peculiarities have thus appeared in a single individual out of many million, all exposed in the same country to the same general conditions of life, and, again, that the same extraordinary peculiarity has sometimes appeared in individuals living under widely different conditions of life, we are driven to conclude that such peculiarities are not directly due to the action of the surrounding conditions, but to unknown laws acting on the organisation or constitution of the individual,—that their production stands in hardly closer relation to the conditions than does life itself."

If we had not domesticated animals and plants, we night probably never have heard of the saying, that "like begeds like"—the proposition would have been self-evident. "Probably no two individuals are identically the same. All wild animals recognise each other, which shows that there is some difference between them."

After citing numerous instances of inherited peculiarities, he says:—

"But it is superfluous to give instances; every shade of expression, which may often be seen alike in parents and children, tells the same story. On what a curious combination of corporeal structure, mental character, and training must handwriting depend! Yet everyone must have noted the occasional close similarity of the handwriting in father and son, although the father had not taught his son. …… Gait, gestures, voice, and general bearing are all inherited, as the illustrious Hunter and Sir A. Carlisle have insisted."

It is needless to dwell upon the examples which ear profession can give of inherited malformations, and of predispositions to disease. We think a predisposition to habits of inebriety is occasionally inherited. There is very little doubt in our own mind that there is in some individuals what we might term a physiological predisposition to it.

Mr. Darwin quotes largely from Mr. Bowman and Mr. White Cooper on inherited imperfections of vision: hypermetropia myopia, amaurosis, colour blindness, and peculiar characters in the colour of the irides, &c. The checks to inheritance, so

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far as we know them, are, firstly, circumstances hostile to the particular character in question; secondly, conditions of life incessantly inducing fresh variability; and; lastly, the crossing of distinct varieties during some previous generation, together with reversion or atavism,—that is, the tendency of the child to resemble its grandparents or more remote ancestors, instead of its immediate parents.

He discusses this subject of Reversion in the next chapter of the volume.

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Reviews and Notices of Books

The Variation of Animals and Plants under Domestication. By CHARLES DARWIN, M.A., F.R.S., &c. Two volumes. London: John Murray, Albemarle-street. 1868.

THIRD NOTICE.

THE sections on the good effects of Crossing, and on the evil effects of Interbreeding, are very full. Manifest evil does not usually follow, says Mr. Darwin, from pairing the nearest relations for two, three, or even four, generations; but several causes interfere with the detection of the evil. He enters but little into this subject in reference to man, on account of the natural prejudices by which it is surrounded; but he dwells upon the fact that marriages between relations seem to be strictly prohibited by all nations. It would be interesting, he says, to get some information as to the higher anthropomorphous apes on this subject; whether any instinctive feeling exists leading them to pair with distinct families rather than with each other. At any rate, it appears to be a great law of Nature that the crossing of animals and plants not closely related to each other is highly beneficial, or even necessary; and that interbreeding prolonged during many generations is highly injurious.

The important phenomena of Hybridism naturally receive full consideration at the author's hands. He evidently feels that the fertility of varieties one with another, and the infertility of natural species, form a great difficulty, although not an overwhelming one. We have no space to follow him through all his arguments. Since the date of his work on the "Origin of Species," he has investigated the fertility of reciprocally dimorphic and trimorphic plants, when illegitimately united, from which he shows that the test of lessened fertility, both in first crosses and in hybrids, is no safe criterion of specific distinction, and obtains illustrations in favour of his conclusion, that the sterility which almost invariably follows the union of distinct species depends exclusively on differences in their sexual constitution. He confesses the very complex nature of the investigation, which is greatly increased by our ignorance in regard to the normal and abnormal action of the reproductive system. But we can see, he thinks, that species, owing to their struggle for life with numerous competitors, must have been exposed to more uniform conditions during long periods of time than have been domestic varieties; and this may well make a wide difference in the result. The chapters on Selection abound with facts and information. The following are interesting, as showing that constitutional peculiarities, entailing liability to the action of certain poisons, are correlated with the colour of the skin. The black colour of the pigs of Virginia is due to the animals feeding upon the roots of a plant which colours their bones pink, and, except in the black varieties, causes their hoofs to drop off. In the Tarentino only black sheep are kept, because a plant which abounds there kills the white ones in about a fortnight's time.

Complexion and liability to certain diseases are believed to run together in man and the lower animals. White terriers suffer most severely from distemper. And the same influences may be traced in the vegetable world. The facts mentioned in regard to the Virginia pigs prove that there is a very wide difference between the chemical and the physiological value of food; and that, chemically speaking, a very nutritious diet table may practically be anything but nutritious. As Mr. G. H. Lewes remarks, in his "Physiology of Common Life," a pound of flesh is enormously superior to a pound of cabbage; yet to a rabbit the cabbage is the superior food, whilst to the dog it is no food at all.

In discussing the Direct and Definite Action of the External Conditions of Life, Mr. Darwin has collected some interesting information, which we give in a somewhat curtailed form:—

"Humboldt remarks that white men born in the torrid zone

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walk barefoot with impunity in the same apartment where a European recently landed is exposed to the attacks of the pulex penetrans. This insect, the well-known chigoe, can then distinguish a difference between the blood and tissue of a European and those of a white man born in the country:— owing, probably, to what Liebig says, that the blood of men with different complexions emits a different odour, though inhabiting the same country.

"Diseases peculiar to certain localities, heights, or climates show the influence of external circumstances on the human body. The Plica Polonica rarely attacks Germans who inhabit the neighbourhood of the Vistula, where so many Poles are grievously affected; but it does not affect Russians, who are said to belong to the same original stock with the Poles. The elevation of a district often governs the appearance of diseases. A peculiar cutaneous complaint, called the Bouton d'Alep, affects in Aleppo and its neighbourhood almost every native infant, and some few strangers. In St. Helena scarlet fever is dreaded like the plague. Analogous facts have been observed in Chili and Mexico. Even in different departments of France it is found that various infirmities which render the conscript unfit for the army prevail with remarkable inequality, showing, as Boudin observes, that many of them are endemic."

Mr. Darwin quotes the people of the United States as an illustration of the changes which may be brought about in a short time, and asks, if emigration into that country were now stopped, who can say that the character of the whole people would not be greatly modified in the course of two or three thousand years?

The facts about the origin of nectarines from peaches, the red and yellow magnum-bonum plum, the deafness of kittens with blue eyes, the influence of climate in modifying diseases, and the action of contagious matters on men and animals, &c., are very interesting reading.

The author has drawn, as we have said, largely upon members of our profession, and the reader will meet with the names of Hunter, Paget, Virchow, Beale, and others.

We have no space to discuss the doctrine of pangenesis, which was in some points maintained by Buffon.

These volumes will be read by a great number of persons for their interest in all that concerns natural history apart from the author's hypothesis altogether, upon the truth of which, after all, it may be an evidence of wisdom to hold the judgment in suspense until fresh facts have been brought to bear upon it.