. Journal of anatomy . rve. The case described by Macphail forms the sole exception, for he says, The cords of the brachial plexus were normal on both sides as regardscontributory nerves. Since the anatomical disposition of the bony and ligamentous portionsin rudimentary first thoracic ribs of class I. is so constant, and the site 382 Mr Frederic Wood Jones of the blending of tlie first and second ribs so uniform in class II., I thinkit is permissible to assume that both these anomalies are produced by adownward pressure caused by the nerve trunk arching over the rib in thesulcus nervi brachia
. Journal of anatomy . rve. The case described by Macphail forms the sole exception, for he says, The cords of the brachial plexus were normal on both sides as regardscontributory nerves. Since the anatomical disposition of the bony and ligamentous portionsin rudimentary first thoracic ribs of class I. is so constant, and the site 382 Mr Frederic Wood Jones of the blending of tlie first and second ribs so uniform in class II., I thinkit is permissible to assume that both these anomalies are produced by adownward pressure caused by the nerve trunk arching over the rib in thesulcus nervi brachialis, and that the extra pressure exerted in these casesis caused, as a rule, by the inclusion of the second thoracic nerve in thebrachial plexus. I believe that the anomaly is seen in the making in thecases of atypical ribs that I have described ; for such a rib, when placed inposition above the next rib in the series, shows a striking resemblance toa case of bicipital rib. The difference in degree of these anomalies I. Fig. 6. —Second thoracic rib showing a well-marked groove forthe intercostal division of the first (or at times the second)thoracic nerve. would ascribe (although as j^et without complete anatomical demonstration)to the varjang contribution from the second thoracic nerve. With examples of cervical ribs, again, a fair amount of evidence isavailable from recorded dissections. Eisler has affirmed that when theseventh cervical rib is found to be well developed, the brachial plexusreceives either no contribution, or only a very insignificant one, from thefirst thoracic nerve. In the great majority of cases where mention ismade of the nerve trunk (without particulars of its constituents), it isdescribed as lying upon the ligament which begins at the site of the nerve,or within the sulcus for the nerve when the cervical rib is fused to thefirst thoracic rib. A particularly interesting case is that described by Black, for he has Relation of Limb Plexuses to Ribs and V
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectanatomy, bookyear1867
