PERICLAVICULAR SUPERNUMERARY MUSCLES 57 



282) describes and figures a supra-clavicular muscle as arising 

 from the middle of the posterior surface of the clavicle and 

 passing over the sternal end of the bone to be inserted into 

 the manubrium sterni just below the inter-clavicular ligament. 

 Luschka suggests a relation between this muscle and the ossa 

 suprasternalia. 



He found the muscle three times in male subjects, once 

 bilateral, twice only on one side. Later (quoted from Gruber, 

 loc. cit., p. 4) Luschka encountered four additional instances of 

 the muscle. 



Hyrtl (" Zwei Varianten des M. Sterno-clavicularis," Sitzber. 

 d. Math, naturw. cl. d. Kais. Akad. der Wiss., Bd. XXIX, 

 Wien, 1858, p. 265) describes Luschka's supra-clavicularis as 

 *' M. sterno-clavicularis " in six subjects out of 83, 5 men and 

 I woman. In four of these (3 bilateral, i on left side) the 

 muscle corresponded to Luschka's description. The two re- 

 maining cases Hyrtl regards as variations of the same muscle. 

 The first variation (subject set. 30) consisted of a tendinous 

 bundle, arising from the manubrium sterni at the level of its 

 junction with the body, which ascended to the jugular notch 

 and divided into two diverging transverse bundles, which, be- 

 coming muscular, passed over the sterno-clavicular joint, behind 

 the clavicular head of the sterno-cleido-mastoid, to the clavicle. 

 The second variation appeared as an intcr-clavicular muscle, a 

 flat transv^erse band uniting the sternal extremities of both 

 clavicles lying upon the inter-clavicular ligament above the upper 

 margin of the manubrium. The muscle was . attached to the 

 sterno-clavicular capsule between the inter-clavicular and sterno- 

 clavicular ligaments and to the intra-articular cartilage of the 

 joint. Hyrtl regards this variation as derived from the first by 

 suppression of the median tendon of origin from the manubrium 

 and by arched fusion of the two muscular bellies thus detached 

 across the median line. 



Other instances of the M. supraclavicularis or stcnioclavi- 

 ciilaris superior are recorded by Retzius (" Hygeia," 1856, 

 Bd. 18, p. 649), Hellema (Geneeskundig Tijdschieft, 5 Jahrg., 

 I Afd.) and Macalister (loc. cit., p. 50). I have observed 13 

 examples of the muscle. 



