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Show 328 LAWS OF VARIATION. CHAP. XXV. these teeth would likewise fail in the infant could not be told. Here is another case communicated to me by 1\'Ir. Wallace on the authority of Dr. Purland, a dentist: Julia Pastrana, a Spanish dancer, was a remarkably fine woman, but she had a thick masculine beard and a hairy forehead ; she was photographed, and her stuffed skin was exhibited as a show ; but what concerns us is, that she had in both the upper and lower jaw an irregular double set of teeth, one row being placed within the other, of which Dr. Purland took a cast. From the redundancy of the teeth her mouth projected, and her face had a gorilla-like appearance. These cases and those of the hairless dogs forcibly call to mind the fact, that the two orders of mammals- namely, the Edentata and Cetacea-which are the most abnormal in their dermal covering, are likewise the most abnormal either by deficiency or redundancy of teeth. The organs of sight and hearing are generally admitted to be homologous, both with each other and with the various dermal appendages; hence these parts are liable to be abnormally affected in conjunction. 1\lr. White Cowper says "that in all cases of " double microphthalmia brought under his notice he has at the " same time met with defective development of the dental sys" tem." Certain forms of blindness seem to be associated with the colour of the hair; a man with black hair and a woman with light-coloured hair, both of sound constitution, married and had nine children, all of whom were born blind ; of these children, five "with clark hair and brown iris were afflicted "with amaurosis; the four others, with light-coloured hair and "blue iris, had amaurosis and cataract conjoined." Several cases could be given, showing that some relation exists between various affections of the eyes and ears; thus Liebreich states that out of 241 deaf-mutes in Berlin, no less than fourteen suffered from the rare disease called pigmentary retinitis. Mr. White Cowper and Dr. Earle have remarked that inability to distinguish different colours, or colour-blindness, "is often "associated with a corresponding inability to distinguish " musical sounds." 20 20 These statements n,re taken from Mr. Sedgwick, in tho 'Medico-Chirurg. Review,' July 1861, p.198; April 1863, pp. 455 and 458. Liebreich is quoted by Professor Devay, in his 'Marin,ges Consanguins,' 1862, p. 116. l CHAP. XXV. CORRELATED VARIABILITY. 329 Here is a more curious case: white cats, if they have blue eyes, are almost always deaf. I formerly thought that the rule was invariable, but I have heard of a few authentic exceptions. The first two notices were published in 1829, and relate to English and Persian cats: of the latter, the Rev. W. T. Bree possessed a female, and he states "that of the offspring pro" duced at one and the same birth, such as, like the mother, "were .entirely white (with blue eyes) were, like her, invariably " deaf; while those that had the least speck of colour on their "fur, as invariably possessed the usual faculty of hearing." 21 The Rev. W. Darwin Fox informs me that he has seen more than a dozen instances of this correlation in English, Persian, and Danish cats; but he adds "that, if one eye, as I have "several times observed, be not blue, the cat hears. On the "other hand, I have never seen a white cat with eyes of the com" mon colour that w.as deaf." In France Dr. Sichel 22 has observed during twenty years similar facts; he adds the remarkable case of the iris beginning, at the end of four months, to grow dark-coloured, and then the cat first began to hear. This case of correlation in cats has struck many persons as marvellous. There is nothing unusual in the relation between blue eyes and white fur; and we have already seen that the organs of sight and hearing are often simultaneously affected. In the present instance the cause probably lies in a slight arrest of development in the nervous system in connection with the sense-organs. Kittens during the first nine days, whilst their eyes are closed, appear to be completely deaf; I have made a great clanging noise with a poker and shovel close to their heads both when th~y were asleep and awake, without producing an; effect. The tnal must not be made by shouting close to their ears, for they are, even when asleep, extremely sensitive to a breath of air. Now, as long as the eyes continue closed, the iris is no doubt blue, for in all the kittens which I have seen this colour remains for some time after the eyelids open. Hence, if we suppose the development of the organs of sight and hearing to be arrested at the stage of the closed eyelids, the eyes would re- 21 Loudon's' Mag. of Nat. Hist.,' vol. i., 1829, pp. 66, 178. See also Dr. P. Lucas, 'L'Hcred. Nat.,' tom. i. p. 428, on the inheritance of deafness in cats. 2•2 'Annales des Sc. Nat.' Zoolog.,3rd series, 1847, tom. viii. p. 23~. |