Essays Upon Heredity and Kindred Biological Problems: Authorised TranslationWeismann, August
Science
Essays Upon Heredity and Kindred Biological Problems: Authorised Translation
Weismann, August
Evolution (Biology); Genetics; Reproduction
When I previously maintained that the proofs of the transmission of
artificially produced diseases are inconclusive, I had in mind the only
experiments which, as far as I am aware, can be adduced in favour of
the transmission of acquired characters; viz. the experiments of
Brown-Séquard[218] on guinea-pigs. It is well known that he produced
artificial epilepsy in these animals by dividing certain parts of the
central and also the peripheral nervous system. The descendants of the
animals which acquired epilepsy sometimes inherited the disease of
their parents.
These experiments have been since repeated by Obersteiner[219], who has
described them in a very exact and entirely unprejudiced manner. The
fact itself cannot be doubted: it is certain that some of the
descendants of animals in which epilepsy has been artificially
produced, have also themselves suffered from epilepsy in consequence of
the disease of their parents. This fact may be accepted as proved, but
in my opinion we have no right to conclude from it that acquired
characters can be transmitted. Epilepsy is not a morphological
character; it is a disease. We could only speak of the transmission of
a morphological character, if a certain morphological change which was
the cause of epilepsy had been produced by the nervous lesion, and if a
similar change had re-appeared in the offspring, and had produced in
them also the symptoms of epilepsy. But that this really occurs is
utterly unproved; and is even highly improbable. It has only been
proved that many descendants of artificially epileptic parents are
small, weakly, and very soon die; and that others are paralysed in
various parts of the body, i. e. in one or both of the posterior or
anterior extremities; while others again exhibit trophic paralysis of
the cornea leading to inflammation and the formation of pus. In
addition to these symptoms, the descendants in very rare cases exhibit
upon the application of certain stimuli to the skin, a tendency towards
those tonic and clonic convulsions together with loss of consciousness
which constitute the features of an epileptic attack. Out of thirty-two
descendants of epileptic parents only two exhibited such symptoms, both
of them being very weakly, and dying at an early age.
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