The significance of anomalies / by Thomas Dwight.

  • Dwight, Thomas, 1843-1911.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: The significance of anomalies / by Thomas Dwight. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the Cebidse. In the case of the third trochanter we can hard- ly stop short of the lemuroidte in spite of the probability that they and the anthropoidre came from a common stem. For a really large para-mastoid process we must go beyond the pri- mates altogether. There would be some comfort to be gained from the insectivora were wTe in the least justified in putting them among the ancestors of the primates, for several genera have a well-developed para-mastoid process, the supra-condy- loid process is general, and the third trochanter is frequently represented, still it is neither general nor very prominent. For its greatest development we must turn to the odd-toed ungulata, and now descent is out of the question. It may be opposed to this that we have no right to assume that a certain well developed anomalous process in man must necessarily be accounted for by inheritance from a form pos- sessing an equal large one; that it is enough to show the existence of a clearly marked process in a common ancestor and to assume that its great development in the anomaly is an accident of no significance. I am quite willing to grant that this objection has weight. Still when we account by atavism for the supra-condyloid process we must admit that the gulf between the structure of man’s body and that of one of the Cebidse is so great that this explanation would hardly serve were it not absolutely necessary for a theory. Another class of anomalies are those, which far from being general features, are found in certain highly specialized ani- mals which can be included in no possible scheme of descent. An instance is the fossa praenasalis, not to be confounded with the rounding of the border of the nares which is practically universal. It occurs in human skulls of a low order and pre- sents a development which is seen in no animal. It is usually more or less distinctly marked in the seal tribe. I have seen it poorly marked in the gorilla. Here atavism is wholly at fault. The Pronator Quadratus muscle in man very rarely sends a prolongation downwards to one or more carpal bones on the radial side of the wrist. I am not aware that this is normal in any mammal. Whence then does it come ? Testut would have it the homologue of a muscle which Humphry