Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley.

  • August Weismann
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    454/476 (page 438)
    brought forward. But if nevertheless such a mysterious mechanism existed between the parts of the body and the germ-cells, by means of which each change in the former could be reproduced in a different manner in the latter, the effects of this marvellous mechanism would certainly be perceptible and could be subjected to experiment. But at p]'esent we have no evidence of the existence of any such effects ; and the experiments described above disprove all the cases of the supposed transmission of single mutilations. Of course, I do not maintain that such cases are to be always explained by want of sufficient observation. In order to make my position clear, I propose to discuss two further classes of observations. First of all, there are very many cases of the ap- parent transmission of mutilations in which it was not the mutila- tion or its consequences which was transmitted, but the predis- position of the part in question to become diseased. Richter ^ has recently pointed out that arrests of development, so slight as to be externally invisible, frequently occur, and that such arrests exhibit a tendency to lead to the visible degeneration of parts in which they occur, as the result of slight injuries. Since therefore the predisposition towards such arrest is transmitted by the germ— occasionally even in an increased degree—the appearance of a trans- mitted injmy may arise. In this way Richter explains, for in- stance, the frequently quoted case of the soldier who lost his left eye by inflammation fifteen years before he was married, and who had two sons with left eyes malformed (microphthalmie). Micro- phthalmia is an arrest of development. The soldier did not lose his eye simply because it was injured, but because it was predis- posed to become diseased from the beginning and readily became inflamed after a slight injury. He did not transmit to his sons the injury or its results, but only microphthalmia, the predis- position towards which was already innate in him, but which led in his sons from the beginning, and without any obvious extemal injury, to the malformation of the eye. I am inclined to explain the case which Darwin in a similar manner adduced, during the later years of his life, in favom- of the transmission of acquired characters, and which seemed to ju-ove that a malformation of the thumb produced by chilblains can be transmitted. The skin of a ' W. Eicliter, ' Zur Vererbung erworbener Charaktere,' Biolog. Centralblatt, Bd. VIII. 1888, p. 289.