This explains why, in Germany, myopia is not a reason for rejection by the examining boards. Since constant study creates myopia, and heredity most frequently perpetuates it, the number of short-sighted persons must necessarily increase in a nation devoted to intellectual pursuits.

2. Anæsthesia of the nerves of sight is transmissible in all its grades and in all its forms. It is a well-known fact that the sensibility of the eye to light is very different in different persons. It may vary as much as 200 per cent., and, of course, will pass through all the intermediate degrees. Heredity transmits these inequalities, from partial to total anesthesia, or blindness, when the eye, incapable of noting form or colour, has only an indistinct perception of light.

Congenital blindness may run in families. Blind persons will sometimes beget blind children. A blind beggar was the father of four sons and a daughter, all blind.1 Dufau, in his work on Blindness, cites the cases of 21 persons blind from birth, or soon after, whose ancestors-father, mother, grandparents, and uncleshad some serious affection of the eyes.

Amaurosis, nyctalopia, and cataract in the parents may become blindness in the children; and such transformations of heredity are not rare in animals.

The incapacity to distinguish colours, known under the name of Daltonism, or colour-blindness, is notoriously hereditary. The distinguished English chemist Dalton was so affected, as were also two of his brothers. Sedgwick discovered that colour-blindness occurs oftener in men than in women. In eight families akin to each other, this affection lasted through five generations, and extended to 71 persons.2

It is readily understood that such an anomaly of vision is not without influence on the mind, at least from the æsthetic point of view. An old man, who had from childhood observed that he could not call the various colours by their names, was grieved because he saw nothing in paintings but what was gray and sombre-in a landscape only an obscure haze, in the sunrise and

1 Lucas, i. 404.

2 Darwin, Variation, etc., ii. p. 70.

sunset, in the brightest tints of the rainbow, and in the grandest scenes of nature, only a cold and dull sameness.

3. There are some persons who seem gifted with extraordinary -almost supernatural-powers of sight. Some cases of this kind are so well attested as scarcely to admit of doubt. Thus, sight at great distances and through opaque substances appears, in some cases, to be proved beyond the possibility of fraud. If there is any explanation of this and other like phenomena, it can only be on the supposition of hyper-æsthesia of the optic nerve.

P. Lucas gives a long account of Hirsch Daenemarck, a Polish Jew, who, about the year 1840, travelled over Europe, showing by decisive experiments that he could read in a closed book any page or line that might be desired.1 This man's son perceived, at about the same age as his father (ten years), that he possessed this same faculty, and perhaps in a more remarkable degree.

It is hardly necessary to observe that heredity always governs vision in its specific form, and that the only room for doubt would be with regard to individual varieties. Thus, all species of animals, from the eagle to the owl-from the earth-worm with its eye-points, to the spider with its facet-eyes-possess a visual apparatus of a structure and optical power peculiar to them, which is preserved and transmitted by heredity like all other specific characters.

III.-OF HEARING.

Though hearing does not possess the same scientific and æsthetic importance as sight, yet it is one of our principal senses. It is the basis of a science-acoustics—and of an art-music; and, what is still more important, on it depends the possibility of articulate language or speech, and, consequently, of deliberate thought. If there be no hearing, there is an end of speech; suppress speech, and thought also is suppressed, with all results.

Hearing, like sight, can have its hyper-æsthesia, its partial and total anesthesia-deafness. As we have seen, there are eyes that cannot distinguish certain colours; in like manner there are ears that cannot hear certain sounds. Wollaston met with persons

1 Lucas, i. pp. 413-419.

who were insensible to all sounds above and below the diatonic scale.

To be congenitally deaf and dumb exerts a well-known and unfortunate influence on the development of the intellect, for which the only remedy is found in the use of artificial signs. If this infirmity is transmissible, heredity may be said to penetrate into the very essence of intellect. But this form of heredity has been disputed.

Dr. Ménière, in a special work on this question, while admitting that in a certain number of instances the direct and immediate heredity of deaf-muteness has been established, says: Nevertheless, these facts must be held to constitute a rare exception; habitually deaf-mutes married to deaf-mutes beget children who hear and speak. This is, of course, still more the case where the marriage is a mixed one, that is, where only one of the couple is deaf and dumb-though even in this case there are well-attested cases of heredity.' Darwin also says:-'When a male or a female deaf-mute marries a sound person, their children are most rarely affected; in Ireland, out of 203 children thus produced only one was mute. Even when both parents have been deafmutes, as in the case of forty-one marriages in the United States, and of six in Ireland, only two deaf and dumb children were produced.' 2

1

We would remark that the returns of the Deaf and Dumb Institution of London, from its foundation to the present time, are conclusive in favour of heredity. Among 148 pupils in that institution at one time, there was one in whose family were five deaf-mutes; another in whose family were four. In the families of II of the pupils there were three each, and in the families of 19, two each.

It is quite possible that, in the case under consideration, the law of heredity is not so much at fault as is commonly supposed. The deaf-muteness of ascendants may, in their descendants, be transformed into an infirmity of some other description, such as hardness of hearing, obtuseness of the mental faculties, or

1 Recherches sur l'Origine de la Surdi-Mutité, par le Docteur Ménière. 2 Variation, etc., ii p. 22.

even idiocy. Of this the distinguished anatomist Menckel gives many instances. But we will consider hereafter this obscure point of the metamorphoses or transformations of heredity.

It has seemed to us more natural to discuss the heredity of the musical faculty under the head of imagination. As will be seen, there is perhaps no other artistic talent that presents more conclusive instances of hereditary transmission (the three Mozarts, the two Beethovens, the more than 120 members of the Bach family). Still, however important the part we assign to the influence of the imagination and of the intellectual faculties, it must be admitted that there can be no musical talent without a certain disposition of the organs of hearing. Here education does next to nothing, for it is nature that gives 'a good ear.' Hence the incontestable heredity of the aptness for music necessarily implies the heredity of certain qualities of hearing. This conclusion applies to performers as well as to composers.

IV. OF SMELL AND TASTE.

It is hardly possible to separate here these two senses, which are so closely allied that smell may be called taste acting at a distance.

Man, no doubt, ranks below other animals as regards fineness of the sense of smell. Nowhere among the human family, even among the negroes, can be found a sense of smell as acute as that of dogs, of carnivorous animals in general, and of certain insects. Gratiolet, in his Anatomie Comparée du Système Nerveux, states that an old piece of wolf-skin, with the hair all worn away, when set before a little dog, threw the animal into convulsions of fear by the slight scent attaching to it. The dog had never seen a wolf; and we can only explain this alarm by the hereditary transmission of certain sentiments, coupled with a certain perception of the sense of smell.

It is notorious that, to a great extent, the value of the canine race depends on their native, and therefore hereditary, subtlety of

scent.

If in animals so highly endowed in this respect we could note individual differences, we should probably see them trans

mitted by heredity. But, unfortunately, we can study them only under the specific form. There, however, there is no room for doubt, for heredity transmits them all without exception.

In the human species, savage races have a characteristic acuteness of smell which allies them to animals. In North America the Indians can follow their enemies or their game by the scent, and in the Antilles the maroon negroes distinguish by the scent a white man's trail from a negro's.1 The whole negro race has this sense developed to an extraordinary degree. Whether this results from a great development of the olfactive membrane, or from the more frequent exercise of this sense, in any case, this innate or acquired faculty is preserved by heredity.

The specific and individual varieties of taste are transmissible, like those of smell. Hybridism gives curious examples of this among animals. 'The swine,' says Burdach, 'has a very strong liking for barley; the wild boar will not touch it, feeding on herbage and leaves. From a cross between a domestic sow and a wild boar come young some of which have an aversion for barley, like the wild boar, while the others have a taste for it, like the common hog.'

In man, anæsthesia of taste, and antipathy for certain flavours, are hereditary. Schook, the author of a treatise entitled De Aversione Casei belonged to a family to nearly all the members of which the smell of cheese was unendurable, and some of whom were thrown into convulsions by it.2 Such antipathy is very often hereditary. In a family of our acquaintance, the father and mother like cheese; the grandmother had an extreme dislike for it. Four of the children share in the same dislike.'3

An exclusive liking for vegetable food and repugnance to flesh is of very rare occurrence, but it is transmissible. A soldier of the Engineers, who derived from his father an invincible repugnance to all food composed of animal substances, was unable, during the 18 months he spent with his regiment, to overcome this aversion, and was obliged to quit the service."

Finally, P. Lucas, following Zimmermann and Gall, gives the

1 Dictionnaire des Sciences Médicales. Art. 'Odorat.'

2 Ibid.

4 Gazette des Tribunaux, 21 Mai, 1844.