A variation that occurs in the manubrium sterni of higher primates / by Arthur Keith.

  • Keith, Arthur, Sir, 1866-1955.
Date:
[1896]
Catalogue details

Licence: Public Domain Mark

Credit: A variation that occurs in the manubrium sterni of higher primates / by Arthur Keith. 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 third costal cartilages implies a very decided change in the formation of the manubrial joint. According to Albrecht, and also to Euge, the manubrium sterni is a composite bone made up of primal elements derived from many bones. Albrecht was of opinion that it always con- tained segments corresponding to ribs belonging to the seventh cervical vertebra. It is evident, if ribs belonging to that verte- bra were present, that the manubrium, as in the hylobatian form, would have 2| pairs of ribs articulating with it on each side. In none of the cases recorded in the above table were seventh cervical ribs present. No explanation of this form of manubrium is derivable from that source. ArlDuthnot Lane, however, suggested that there was a segment intercalated be- tween the dorsal and cervical regions, and that the extra piece of the manubrium sterni in the hylobatian form belonged to the intercalated segment. There were really eight cervical vertebraj, and the eighth carried a rib. This theory was countenanced by the presence of a large strand from the tenth spinal nerve join- ing the brachial plexus. Such an addition to tlie brachial plexus, however, is not unfrequently found when there is no reason to suppose that there is an intercalated segment. The number of ribs, also, does not particularly favour Arbuthnot Lane’s theory. Most frequently there is no increase in the number of ribs accompanying the hylobatian form of manu- brium. In the case recorded by him there were thirteen ribs, eight of which reached the sternum. In two of the other cases recorded of Man there were eight sternal ribs, but only the usual number of twelve ribs in all. In the Gorilla and Chim- panzee eight sternal ribs occur more frequently in animals with a hylobatian form of manubrium than with the more usual form; but in Gibbons neither the total number of ribs, nor the number of sternal ribs, seem to be affected by the occurrence of the enlarged form of manubrium. In that genus the number of sternal ribs varies. from six to eight, seven being the most common. This form of sternum, so far as my material goes, is not more prevalent in one species of Hylobates than in another. In conclusion, I beg to take this occasion of acknowledging my indebtedness to the authorities of the South Kensington