ESSAYS ON PHYSIOLOGICAL SUBJECTS.* TUE first three of these essays,

viz., those on "Marriages of Consanguinity," on "The Production of Low Organisms," and on "The Production of Organisms in Closed Vessels," have been already submitted to the public in the first edition of this work, published rather more prematurely than the author wished in 1868. To these have been added in this, the second edition, an essay on "Some Aspects of the Theory of Evolution," concerning which

* Essays on Physiological Sukiects. By Gilbert W. Child. London: Longmans, Green, and Co.

the author congratulates himself on the coincidence of his views with those expressed by Professor Owen in the concluding chapter of his " Anatomy of the Vertebrate; " one denominated

"Physiological Experiments," in which Dr. Child deprecates a too universal condemnation of vivisection ; and lastly, an essay on

" Physiological Psychology," written -with the view of rendering intelligible to such as have interested themselves nearly exclusively in the metaphysical or subjective study of psychology, the latest results of anatomical investigation bearing thereon. Dr. Child's labour, especially in the first three and fifth essays, has rather con- sisted in judicious selection of recently determined facts, and their clear arrangement for deduction of conclusions, than in the produc- tion of new facts or the suggestion of new theories. The subjects are, however, such as demand for such selection expert judg- ment in dealing with the confused and voluminous details which have been accumulated within the last few years in relation to them, and we have much pleasure in testifying to the thorough- ness with which this end has been achieved in the volume now under our notice.

In the first essay, that on "Marriages of Consanguinity," Dr.

Child may be held to have fairly established his " demonstranda" in their favour. Before, however, giving any exaggerated idea of the importance of his effort, it will be well to consider what pre- cisely he has attempted to prove. So little has of late been advanced in favour of consanguineous marriages, that the popular view condemnatory of them has attained a certain authority by long standing. At first Dr. Child seemed to us to have courted the onerous task of overcoming this. He remarks that since, until the Marriage Act of 1540 such unions were legally, and have after it been still theologically, objectionable,

—" nothing could be more natural, especially in an age when men were much more open to theological than physiological considerations, than that they should attribute any ill effects which might seem to follow from such unions to the special interventions of Providence. Such ill effects would be marked and noticed whenever they occurred, and would soon become proverbial, and when in a later age men began to pay more attention to the bleeding of animals, and found that excessively close breeding seemed in some eases to produce similar results, they would be led to establish a false analogy between the two cases, and to infer the existence of a law of nature which close breeding and consanguineous marriages equally infringed."

Would not the reader be induced to conclude from this that Dr. Child considers the apparent analogy between close breeding in animals and consanguineous marriages false, and that he does not hold that the latter cause an infringement of a natural law which would be productive of injury to man ? Other passages would confirm such a conclusion. Yet nothing is farther from Dr. Child's purpose than to dispute the effect which such marriages have in intensifying the defects, though probably also the strong qualities, in the constitu- tions of members of a family, or in a smaller degree of a race. For obvious reasons, no family can afford to intensify the latter at the expense of also intensifying the first. No chain is stronger than its weakest link, nor will certain unusually healthy organs avail in general against others unusually defective to prevent the dissolution of the organism. That consanguineous marriages are as a rule productive of injurious consequences remains, therefore, as uncontroverted a truth as before. All Dr. Child attempts to establish is this,—that the ordinary laws of inheritance and their consequences admitted, there is nothing else in such unions to lead to injurious results. It might at first appear to many that this proposition will be undisputed. There can be no meaning in an assertion that consanguinity as consanguinity is injurious. It is the case, however, that a view has been entertained by certain French savants, though, we expect, with much less assurance and tenacity than that Dr. Child repro- bates, that there is something special in the consequent non- renewal of the blood which operates injuriously. We do not feel satisfied that this is at all prominently advocated. The one passage, however, which Dr. Child quotes is downright enough :—

" Co qu'on reprocho ads manages consangnines ce n'est pas, dit le docteur Dechambre, de perpetuer dans les fiunilles par le moyen des alliances lea maladies susceptibles de transmission hereditaire en

certaines predispositions organiques On accuse lee alliances entre parents de memo source d'amener do creer par he soul fait de non renouvellement de sang, une cause special de degradation organique, fatale a la propagation de fespece."

This is quoted by Dr. Devay with approbation, but how far the other French writers adopt the same view is not so clear. Their

doing so cannot be reconciled with their argument in objection to applying in the case of man the results of experiments upon cattle. It is objected that the healthy results of close breeding among cattle are due to the systematic selection of healthy parents by the breeders. This is clearly no objection, as is noticed by Dr. Child, on the part of those who assert that the simple non-renewal of blood is itself an efficient cause, be the parents healthy or not. That Mr. Darwin can be shown to have advocated such a doctrine we feel still less satisfied. Certainly nothing that is herein quoted from his works, nor anything we have met with in them, would tend to commit him to the opinion that perfectly healthy parents would, from mere kindredness of nature, the one with the other, produce an unhealthy offspring.

Supposing, however, that this doctrine be really promi- nently advocated, Dr. Child may be held, we think, to

have very effectually shaken it. He asks, in the first place, if the effects which have been attributed to this cause, this non-renewal of the blood owing to consanguineous union taken as a cause of evil in itself, cannot be equally well explained by the action of the ordinary laws of inheritance. Dr. Bemiss has shown that out of 34 consanguineous marriages 27 only have proved fruitful, while the total number of children resulting from them has been 192. This gives 5.6 as the average number of children to each marriage, while the average number of births to each marriage in England was recently 4.5. If it is safe to draw a conclusion from so limited statistics, these unions appear to be peculiarly fruitful. Of these 192 children 58 died in early life, i.e., the number of early deaths was as 1 to 3.3. Dr. West gives the general averege as 1 to 3. The infant mortality is then rather less than that in the case of marriages generally. The statistics of Dr. Howe and Dr. Devay lead, as far as they go, in the same direction. M. Boudin, however, whose statistics are on a much larger scale, has arrived at the following startling results :—He finds that while consanguineous marriages are 2 per cent. of all marriages in France, the number of deaf mutes born of such marriages is, to all deaf mutes, in Lyons, 25 per cent. ; in Paris, 28; and in Bordeaux, 30; also, that the danger of deaf-and- dumb offspring increases with the nearness of kinship between the parents ; that the number of deaf mutes increases with the local difficulties to freedom of cross-marrying ; that the defect cannot be explained by the ordinary laws of inheritance, for that parents themselves deaf and dumb do not usually produce deaf and dumb offspring. That these results may be said to confirm the opinion concerning the danger of such unions is clear enough. But that their cause is other than the intensifying of vicious predispositions remains absolutely unsupported, except by the last proposition denying the transmissibility of deaf mutism. But when it is considered how little necessary to his position it is that the pre- disposition in the parent should be of the same kind as its result in the issue (Dr. Child mentions that in cats, blue eyes in the ancestor are an indication, and often the only one, of a tendency which will result in deafness in the progeny) ; how constantly therefore the presence of vicious tendencies will be overlooked ; how often the defects remain latent for one or more generations, and how hardly will natural motives to secrecy on such.matters permit the revelation by members of a family of even ascertained family taints ; Dr. Child considers that this cannot be looked upon as a potent argument for his opponents. On the other hand, he maintains that the great diversity of the diseases consequent upon consanguineous marriages, as sterility, mutism, idiocy, deformity, and scrofula, point to some considerable diver- sity in the causes, while the alleged consanguinity pure is a simple one. Moreover, these effects all occur where no such marriage has been contracted, and are all absent far more often than present when it has. But the strongest argument is that afforded by the breeding of animals, in which the closest intercrossiug is constantly combined with the most perfect freedom from any physical taint whatsoever. Of course this is no peculiar recom- mendation to close breeding. It is merely the result of the selection of perfectly healthy parents, and can only be urged as an argument against the doctrine of mere non-renewal, of the blood, however healthy, being in itself pernicious. It will be enough to cite the instance given of the celebrated bull " Comet." This animal rejoices in a pedigree about as paralyzing to the ordinary intellect as the intricacies of Governor Eyre's trial were to the cabman who nearly drove Artemus Ward into the Thames. Comet's grandsire, Phoenix, was his great-grandsire also. His dam and grand-dam were one individual by name, Favourite, while his great-grand-dam and great grandsire were both the offspring of the same parent, Foljarnbe. Three individuals, therefore, at most compose his whole number of ancestors of the fourth degree, while the normal number to each individual may be said to be sixteen. The non-renewal of the blood is, therefore, in this instance nearly at a maximum. Yet the only object of all this close breeding was, of course, perfection of physique. This cannot be said either to be an extreme and exceptional instance :— "M. Beaudonin also, in a memoir to be found in the Comptes Rendza of August 5, 1862, gives some very interesting particulars of a flock of Merino sheep, bred in and in for a period of twenty-two years without a single cross, and with perfectly successful results, there being no sign of decreased fertility and the breed having in other respects improved."

Before dismissing the subject, Dr. Child enters a protest against the espousal by Darwin of the opposite view. To our mind, how- ever, this espousal is rather apparent than real.. Mr. Darwin

states at the commencement of his valuable work on the Fertiliza- tion of Orchids, "It is apparently a universal law of nature that

organic beings require an occasional cross with another individual."' He more particularly favours this inference after noticing how little is self-fertilization the rule even among certain orchids, which are so furnished with elaborate appliances for the economy of their precious seed as in them peculiarly to induce us to expect it.

The juxtaposition of the stigma and pollinia in thesame flower would directly facilitate it. Yet the fertilization is carried on chiefly through the medium of insects who transport the pollen from one flower to another, and is prevented by preventing the visits of the insects. If Mr. Darwin had intended to establish from these facts not simply the probability of deterioration by close breeding, but the uncompromising doctrine of Dr. Devay, his argument would have assumed this peculiar form. Although self-fertilization is the rule in the vegetable kingdom, still there are a few genera which would perish if dependent upon it, though these also have self-fertilizing species. Therefore nature is unfavourable to self- fertilization. Therefore nature is unfavourable to close breeding amongst animals. Therefore one of the incidents of con- sanguineous unions, viz., the non-renewal of the blood, is the pernicious element.

We have not space to notice the remaining essays in this volume.

But we think they will reward study. They are marked by care- fulness, accuracy, and an uncompromising spirit of true inquiry, with that clearness and directness of style which such a spirit does not fail to generate.