418 Proceedings of the Royal Irish Academy. 



I have met witli one case. I have never seen the more frequent form 

 of this anomaly. 



Supra-clavicula/ris ; sterno-clamciilaris (Hyrtl) ; sterno-clavicularis 

 superior; sterno-omoideus. — Arises from anterior surface of manubrium 

 sterni, and is inserted, into the front of the clavicle at a variable dis- 

 tance from its outer end. "When symmetrically developed, the two 

 muscles often meet in the middle line, forming a 



Musmlus inter clavicularis. — Of this latter form of the anomaly I 

 have seen two examples. I have observed but one specimen of uni- 

 lateral development. 



Retro-clavicularis ("Weber) ; sterno-clavicularis postictis. — Arises from 

 posterior surface of manubrium sterni, and is inserted into the inner 

 end of the clavicle, on its posterior surface. I have seen one speci- 

 men, but it had, as in the one observed by Lawson Tait, a second head 

 from the posterior sterno-clavicular ligament. 



Infra- clavicularis (Bardeleben). — Arises from front of clavicle, and 

 is inserted into the fascia in front of the pectoralis major. I have 

 met with one example : it arose fleshy from the clavicle for about an 

 inch of the middle of its anterior border and formed a tendinous ex- 

 pansion, which, passing downwards and outwards, and intersecting, 

 at a very acute angle, the line of direction of the clavicular fibres of 

 the pectoralis major, bended with the fascia, in front of the latter 

 muscle, after a course — including the length of the fleshy fibres — of 

 about four inches. So far as I know, this is the only example pub- 

 lished, except that of Bardeleben. 



Subclavius posticus ; scapido-costalis ; sterno-scapularis. — Arises from 

 the first rib, and is inserted into the root of the coracoid process of the 

 scapula, or into the ligament of the notch. I have seen but one 

 example occurring in a large number of subjects, having examined 

 this region carefully for anomalies, in over a hundred. Krause says 

 the frequency of its occurrence averages seven per cent., and according 

 to Professor Macalister it is met with once in fifteen subjects. 



&upra-costalis superficialis (vel anterior). — A bundle of muscular 

 fibres passing from one of the upper ribs (generally the first) to 

 another rib at a variable distance below. It lies beneath the pec- 

 toralis major and minor. 



Supra-costalis profundus. — This bundle of fibres, when present, lies 

 beneath the serratus anticus magnus. I have met with a good many 

 specimens of both superficialis and profundus, but did not feel suffi- 

 ciently interested in the anomaly to keep any record of them. 



Transversus colli (Luschka); costo-fascialis c^mm/^s (Macalister). — 

 This muscle arises from the first rib, and passing obliquely inwards 

 behind the clavicle, and between the sterno-hyoid and sterno-thyroid 

 muscles, is inserted into the deep fascia at the root of the neck (sep- 

 tum thoracico-cervicale). Professor Krause suggests that it may be 

 regarded as an upper differentiated digitation of the triangularis sterni 

 muscle. 



Tensor semivuginae articulationis humero-seapularis (Gruber). — This 



