Chapter XII: Inheritance (2)

In most of the cases of inheritance recorded by Brown-Séquard only one of the two parents had been operated upon and was affected. He concludes by expressing his belief that “what is transmitted is the morbid state of the nervous system,” due to the operation performed on the parents.

With the lower animals Dr. Prosper Lucas has collected a long list of inherited injuries. A few instances will suffice. A cow lost a horn from an accident with consequent suppuration, and she produced three calves which were hornless on the same side of the head. With the horse, there seems hardly a doubt that exostoses on the legs, caused by too much travelling on hard roads, are inherited. Blumenbach records the case of a man who had his little finger on the right hand almost cut off, and which in consequence grew crooked, and his sons had the same finger on the same hand similarly crooked. A soldier, fifteen years before his marriage, lost his left eye from purulent ophthalmia, and his two sons were microphthalmic on the same side.[59] In all cases in which a parent has had an organ injured on one side, and two or more of the offspring are born with the same organ affected on the same side, the chances against mere coincidence are almost infinitely great. Even when only a single child is born having exactly the same part of the body affected as that of his injured parent, the chances against coincidence are great; and Professor Rolleston has given me two such cases which have fallen under his own observation,—namely of two men, one of whom had his knee and the other his cheek severely cut, and both had children born with exactly the same spot marked or scarred. Many instances have been recorded of cats, dogs, and horses, which have had their tails, legs, etc., amputated or injured, producing offspring with the same parts ill-formed; but as it is not very rare for similar malformations to appear spontaneously, all such cases may be due to coincidence. It is, however, an argument on the other side that “under the old excise laws the shepherd-dog was only exempt from tax when without a tail, and for this reason it was always removed;”[60] and there still exist breeds of the shepherd-dog which are always born destitute of a tail. Finally, it must be admitted, more especially since the publication of Brown-Séquard’s observations, that the effects of injuries, especially when followed by disease, or perhaps exclusively when thus followed, are occasionally inherited.[61]

_Causes of Non-inheritance._

A large number of cases of non-inheritance are intelligible on the principle, that a strong tendency to inheritance does exist, but that it is overborne by hostile or unfavourable conditions of life. No one would expect that our improved pigs, if forced during several generations to travel about and root in the ground for their own subsistence, would transmit, as truly as they now do their short muzzles and legs, and their tendency to fatten. Dray-horses assuredly would not long transmit their great size and massive limbs, if compelled to live on a cold, damp mountainous region; we have indeed evidence of such deterioration in the horses which have run wild on the Falkland Islands. European dogs in India often fail to transmit their true character. Our sheep in tropical countries lose their wool in a few generations. There seems also to be a close relation between certain peculiar pastures and the inheritance of an enlarged tail in fat-tailed sheep, which form one of the most ancient breeds in the world. With plants, we have seen that tropical varieties of maize lose their proper character in the course of two or three generations, when cultivated in Europe; and conversely so it is with European varieties cultivated in Brazil. Our cabbages, which here come so true by seed, cannot form heads in hot countries. According to Carrière,[62] the purple-leafed beech and barberry transmit their character by seed far less truly in certain districts than in others. Under changed circumstances, periodical habits of life soon fail to be transmitted, as the period of maturity in summer and winter wheat, barley, and vetches. So it is with animals: for instance, a person, whose statement I can trust, procured eggs of Aylesbury ducks from that town, where they are kept in houses and are reared as early as possible for the London market; the ducks bred from these eggs in a distant part of England, hatched their first brood on January 24th, whilst common ducks, kept in the same yard and treated in the same manner, did not hatch till the end of March; and this shows that the period of hatching was inherited. But the grandchildren of these Aylesbury ducks completely lost their habit of early incubation, and hatched their eggs at the same time with the common ducks of the same place.

Many cases of non-inheritance apparently result from the conditions of life continually inducing fresh variability. We have seen that when the seeds of pears, plums, apples, etc., are sown, the seedlings generally inherit some degree of family likeness. Mingled with these seedlings, a few, and sometimes many, worthless, wild-looking plants commonly appear, and their appearance may be attributed to the principle of reversion. But scarcely a single seedling will be found perfectly to resemble the parent-form; and thus may be accounted for by constantly recurring variability induced by the conditions of life. I believe in this, because it has been observed that certain fruit-trees truly propagate their kind whilst growing on their own roots; but when grafted on other stocks, and by this process their natural state is manifestly affected, they produce seedlings which vary greatly, departing from the parental type in many characters.[63] Metzger, as stated in the ninth chapter, found that certain kinds of wheat brought from Spain and cultivated in Germany, failed during many years to reproduce themselves truly; but at last, when accustomed to their new conditions, they ceased to be variable,—that is, they became amenable to the power of inheritance. Nearly all the plants which cannot be propagated with any approach to certainty by seed, are kinds which have been long propagated by buds, cuttings, offsets, tubers, etc., and have in consequence been frequently exposed during what may be called their individual lives to widely diversified conditions of life. Plants thus propagated become so variable, that they are subject, as we have seen in the last chapter, even to bud-variation. Our domesticated animals, on the other hand, are not commonly exposed during the life of the individual to such extremely diversified conditions, and are not liable to such extreme variability; therefore they do not lose the power of transmitting most of their characteristic features. In the foregoing remarks on non-inheritance, crossed breeds are of course excluded, as their diversity mainly depends on the unequal development of character derived from either parent or their ancestors.

_Conclusion._

It has been shown in the early part of this chapter how commonly new characters of the most diversified nature, whether normal or abnormal, injurious or beneficial, whether affecting organs of the highest or most trifling importance, are inherited. It is often sufficient for the inheritance of some peculiar character, that one parent alone should possess it, as in most cases in which the rarer anomalies have been transmitted. But the power of transmission is extremely variable. In a number of individuals descended from the same parents, and treated in the same manner, some display this power in a perfect manner, and in some it is quite deficient; and for this difference no reason can be assigned. The effects of injuries or mutilations are occasionally inherited; and we shall see in a future chapter that the long-continued use and disuse of parts produces an inherited effect. Even those characters which are considered the most fluctuating, such as colour, are with rare exceptions transmitted much more forcibly than is generally supposed. The wonder, indeed, in all cases is not that any character should be transmitted, but that the power of inheritance should ever fail. The checks to inheritance, as 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 in the child to resemble its grand-parents or more remote ancestors instead of its immediate parents. This latter subject will be discussed in the following chapter.

REFERENCES

[1] ‘Medical Notes and Reflections,’ 3rd edit., 1855, p. 267.

[2] Mr. Buckle, in his ‘History of Civilisation,’ expresses doubts on the subject, owing to the want of statistics. _See also_ Mr. Bowen, Professor of Moral Philosophy, in ‘Proc. American Acad. of Sciences,’ vol. v. p. 102.

[3] For greyhounds, _see_ Low’s ‘Domestic Animals of the British Islands,’ 1845, p. 721. For game-fowls, _see_ ‘The Poultry Book,’ by Mr. Tegetmeier, 1866, p. 123. For pigs, _ see_ Mr. Sidney’s edition of ‘Youatt on the Pig,’ 1860, pp. 11, 22.

[4] ‘The Stud Farm,’ by Cecil, p. 39.

[5] ‘Philosophical Transactions,’ 1755, p. 23. I have seen only second-hand accounts of the two grandsons. Mr. Sedgwick, in a paper to which I shall hereafter often refer, states that _ four_ generations were affected, and in each the males alone.

[6] Barbara Van Beck, figured, as I am informed by the Rev. W.D. Fox, in Woodburn’s ‘Gallery of Rare Portraits,’ 1816, vol. ii.

[7] ‘Proc. Zoolog. Soc.,’ 1833, p. 16.

[8] Hofacker ‘Ueber die Eigenschaften,’ etc., 1828, s. 34. With respect to France, Report by Pariset in ‘Comptes Rendus,’ 1847, p. 592.

[9] Hunter, as quoted in Harlan’s ‘Med. Researches,’ p. 530. Sir A. Carlisle, ‘Phil. Transact.,’ 1814, p. 94.

[10] Girou de Buzareingues, ‘De la Génération,’ p. 282. I have given an analogous case in my book on ‘The Expression of the Emotions.’

[11] The works which I have read and found most useful are Dr. Prosper Lucas’s great work, ‘Traité de l’Hérédité Naturelle,’ 1847; Mr. W. Sedgwick, in ‘British and Foreign Medico-Chirurg. Review,’ April and July, 1861, and April and July, 1863: Dr. Garrod on Gout is quoted in these articles. Sir Henry Holland, ‘Medical Notes and Reflections,’ 3rd edit., 1855. Piorry, ‘De l’Hérédité dans les Maladies,’ 1840. Adams, ‘A Philosophical Treatise on Hereditary Peculiarities,’ 2nd edit., 1815. Essay on ‘Hereditary Diseases,’ by Dr. J. Steinan, 1843. _See_ Paget in ‘Medical Times,’ 1857, p. 192, on the Inheritance of Cancer; Dr. Gould, in ‘Proc. of American Acad. of Sciences,’ Nov. 8th, 1853, gives a curious case of hereditary bleeding in four generations. Harlan, ‘Medical Researches,’ p. 593.

[12] Marshall, quoted by Youatt in his work on Cattle, p. 284.

[13] Almost any other organ might have been selected. For instance Mr. J. Tomes, ‘System of Dental Surgery,’ 2nd edit., 1873, p. 114, gives many instances with teeth, and others have been communicated to me.

[14] ‘Philosoph. Transact.,’ 1814, p. 94.

[15] ‘Medical Notes and Reflections,’ 3rd edit., p. 33.

[16] This affection, as I hear from Mr. Bowman, has been ably described and spoken of as hereditary by Dr. Donders of Utrecht, whose work was published in English by the Sydenham Society in 1864.

[17] M. Giraud-Teulon has recently collected abundant statistical evidence, ‘Revue des Cours Scientifiques,’ Sept., 1870, p. 625, showing that short sight is due to the habit of viewing objects from a short distance, _c’est le travail assidu, de près._

[18] Quoted by Mr. Herbert Spencer, ‘Principles of Biology,’ vol. i. p. 244.

[19] ‘British and Foreign Medico-Chirurg. Review,’ April, 1861, pp. 482-6; ‘L’Héréd. Nat.,’ tom. i. pp. 391-408.

[20] Dr. Osborne, Pres. of Royal College of Phys. in Ireland, published this case in the ‘Dublin Medical Journal,’ for 1835.

[21] These various statements are taken from the following works and papers:—Youatt on ‘The Horse,’ pp. 35, 220. Lawrence, ‘The Horse,’ p. 30. Karkeek, in an excellent paper in ‘Gard. Chronicle,’ 1853, p. 92. Mr. Burke, in ‘Journal of R. Agricul. Soc. of England,’ vol. v. p. 511. ‘Encyclop. of Rural Sports,’ p. 279. Girou de Buzareingues, ‘Philosoph. Phys.,’ p. 215. _ See_ following papers in ‘The Veterinary;’ Roberts in vol. ii. p. 144; M. Marrimpoey vol. ii. p. 387; Mr. Karkeek, vol. iv. p. 5; Youatt on Goitre in Dogs, vol. v. p. 483: Youatt in vol. vi. pp. 66, 348, 412; M. Bernard, vol. xi. p. 539; Dr. Samesreuther, on Cattle, in vol. xii. p. 181; Percivall, in vol. xiii. p. 47. With respect to blindness in horses _see also_ a whole row of authorities in Dr. P. Lucas’s great work, tom. i. p. 399. Mr. Baker in ‘The Veterinary,’ vol. xiii. p. 721, gives a strong case of hereditary imperfect vision and of jibbing.

[22] Knight on ‘The Culture of the Apple and Pear,’ p. 34. Lindley’s ‘Horticulture,’ p. 180.

[23] These statements are taken from the following works in order:—Youatt on ‘The Horse,’ p. 48; Mr. Darvill, in ‘The Veterinary,’ vol. viii. p. 50. With respect to Robson, _see_ ‘The Veterinary,’ vol. iii. p. 580; Mr. Lawrence on ‘The Horse,’ 1829, p. 9; ‘The Stud Farm,’ by Cecil, 1851; Baron Cameronn, quoted in ‘The Veterinary,’ vol. x. p. 500.

[24] ‘Recreations in Agriculture and Nat. Hist.,’ vol. i. p. 68.

[25] ‘Ueber die Eigenschaften,’ etc., 1828, s. 107.

[26] Bronn’s ‘Geschichte der Natur,’ Band ii. 2 s. 132.

[27] Vrolik has discussed this point at full length in a work published in Dutch, from which Sir J. Paget has kindly translated for me passages. _See, also,_ Isidore Geoffroy St. Hilaire’s ‘Hist. des Anomalies,’ 1832, tom. i. p. 684.

[28] ‘Massachusetts Medical Society,’ vol. ii. No. 3; and ‘Proc. Boston Soc. of Nat. Hist.,’ vol. xiv. 1871, p. 154.

[29] Dr. J. W. Ogle gives a case of the inheritance of deficient phalanges during four generations. He adds references to various recent papers on inheritance, ‘Brit. and For. Med.-Chirurg. Review,’ April 1872.

[30] For these several statements, _see_ Dr. Struthers ‘Edinburgh New Phil. Journal,’ July, 1863, especially on intermissions in the line of descent. Prof. Huxley, ‘Lectures on our Knowledge of Organic Nature,’ 1863, p. 97. With respect to inheritance, _see_ Dr. Prosper Lucas, ‘L’Hérédité Nat.,’ tom. i. p. 325. Isid. Geoffroy, ‘Anom.,’ tom. i. p. 701. Sir A. Carlisle, in ‘Phil. Transact.,’ 1814, p. 94. A. Walker, on ‘Intermarriage,’ 1838, p. 140, gives a case of five generations; as does Mr. Sedgwick in ‘Brit. and Foreign Medico-Chirurg. Review,’ April, 1863, p. 462. On the inheritance of other anomalies in the extremities _see_ Dr. H. Dobell, in vol. xlvi. of ‘Medico-Chirurg. Transactions,’ 1863; also Mr. Sedgwick in op. cit., April, 1863, p. 460. With respect to additional digits in the negro _see_ Prichard, ‘Physical History of Mankind.’ Dr. Dieffenbach (‘Jour. Royal Geograph. Soc.,’ 1841, p. 208) says this anomaly is not uncommon with the Polynesians of the Chatham Islands; and I have heard of several cases with Hindus and Arabs.

[31] Meckel and Isid G. St. Hilaire insist on this fact. _See also_ M. A. Roujou, ‘Sur quelques Analogies du Type Humain,’ p. 61; published, I believe, in the ‘Journal of the Anthropolog. Soc. of Paris,’ Jan. 1872.

[32] ‘The Poultry Chronicle,’ 1854, p. 559.

[33] The statements in this paragraph are taken from Isidore Geoffroy St. Hilaire, ‘Hist. des Anomalies,’ tom. i. pp. 688-693. Mr. Goodman gives, ‘Phil. Soc. of Cambridge,’ Nov. 25th, 1872, the case of a cow with three well developed toes on each hind limb, besides the ordinary rudiments; and her calf by an ordinary bull had extra digits. This calf also bore two calves having extra digits.

[34] ‘Medical Notes and Reflections,’ 1839, pp. 24, 34. _See also_ Dr. P. Lucas, ‘L’Héréd. Nat.,’ tom. ii. p. 33.

[35] ‘Du Danger des Mariages Consanguins,’ 2nd edit., 1862, p. 103.

[36] ‘British and Foreign Medico-Chirurg. Review,’ July, 1863, pp. 183, 189.

[37] Verlot ‘La Product. des Variétés,’ 1865, p. 32.

[38] Loudon’s ‘Gardener’s Mag.,’ vol. xii. 1836, p. 368.

[39] Verlot, ‘La Product. des Variétés,’ 1865, p. 94.

[40] Bronn’s ‘Geschichte der Natur,’ B. ii. s. 121. Mr. Meehan makes a similar statement in ‘Proc. Nat. of Philadelphia,’ 1872, p. 235.

[41] Rev. W. A. Leighton, ‘Flora of Shropshire,’ p. 497; and Charlesworth, ‘Mag. of Nat. Hist.,’ vol. i. 1837, p. 30. I possess prostrate trees produced from these seeds.

[42] Verlot, op. cit., p. 93.

[43] For these several statements, _see_ Loudon’s ‘Gard. Magazine,’ vol. x. 1834, pp. 408, 180; and vol. ix. 1833, p. 597.

[44] These statements are taken from Alph. De Candolle, ‘Bot. Géograph.,’ p. 1083.

[45] Verlot, op. cit., p. 38.

[46] Op. cit., p. 59.

[47] Alph. De Candolle, ‘Géograph. Bot.,’ p. 1082.

[48] _See_ ‘Cottage Gardener,’ April 10th, 1860, p. 18, and Sept. 10th, 1861, p. 456; ‘Gardener’s Chronicle,’ 1845, p. 102.

[49] Darwin in ‘Journal of Proc. Linn. Soc. Bot.,’ 1862, p. 94.

[50] Hofacker, ‘Ueber die Eigenschaften,’ etc., s. 10.

[51] Bechstein, ‘Naturgesch. Deutschlands,’ B. iv. s. 462. Mr. Brent, a great breeder of canaries, informs me that he believes that these statements are correct.

[52] ‘The Poultry Book,’ by W. B. Tegetmeier, 1866, p. 245.

[53] ‘British and Foreign Med.-Chirurg. Review,’ July, 1861, pp. 200-204. Mr. Sedgwick has given such full details on this subject, with ample references, that I need refer to no other authorities.

[54] Mr. Sproule, in ‘British Medical Journal,’ April 18th, 1863.

[55] ‘De l’Espèce,’ tom. ii. 1859, p. 299.

[56] Nevertheless Mr. Wetherell states, ‘Nature,’ Dec. 1870, p. 168, that when he visited fifteen years ago the Sioux Indians, he was informed “by a physician, who has passed much of his time with these tribes, that sometimes a child was born with these marks. This was confirmed by the U.S. Government Indian Agent.”

[57] ‘Philosoph. Mag.,’ vol. iv. 1799, p. 5.

[58] ‘Proc. Royal Soc.,’ vol. x. p. 297. ‘Communication to the Brit. Assoc.,’ 1870. ‘The Lancet,’ Jan. 1875, p. 7. The extracts are from this last paper. It appears that Obersteiner, ‘Stricker’s Med. Jahrbücher,’ 1875, No. 2, has confirmed Brown-Séquard’s observations.

[59] This last case is quoted by Mr. Sedgwick in ‘British and Foreign Medico-Chirurg. Review,’ April, 1861, p. 484. For Blumenbach, _see_ above-cited paper. _See also_ Dr. P. Lucas, ‘Traité de l’Héréd. Nat.,’ tom. ii. p. 492. Also, ‘Transact. Linn. Soc.,’ vol. ix. p. 323. Some curious cases are given by Mr. Baker in the ‘Veterinary,’ vol. xiii. p. 723. Another curious case is given in the ‘Annales des Scienc. Nat.,’ 1st series, tom. xi. p. 324.

[60] ‘The Dog,’ by Stonehenge, 1867, p. 118.

[61] The Mot-mot habitually bites the barbs off the middle part of the two central tail-feathers, and as the barbs are congenitally somewhat reduced on the same part of these feathers, it seems extremely probable, as Mr. Salvin remarks (‘Proc. Zoolog. Soc.’ 1873, p. 429), that this is due to the inherited effects of long-continued mutilation.

[62] ‘Production et Fixation des Variétés,’ 1865, p. 72.

[63] Downing, ‘Fruits of America,’ p. 5: Sageret, ‘Pom. Phys.,’ pp. 43, 72.