56 HUNTINGTON 



Paris, 1884, p. 55) and Le Double (" Traite des variations du 

 systeme musculaire de riiomme," Tome I, Paris, 1897, p. 

 266) quote Weber's and Tait's cases — under the name of " J/. 

 retro-clavicidaris'' or '' Sterno-clavicularis posterior'" — without 

 adding any new instances of the variation. 



In the interests of a consistent terminology it would ap- 

 pear advisable to describe Weber's case as a '' M. sterno- 

 clavicidaris posterior,'' Tait's instance as " M. cJiondro-sterno- 

 clavicidaris posterior,'' the fiv^e cases of superficial muscles above 

 quoted as examples of the '* M. siipra-clavicnlaris propriiis 

 anterior" and the muscles here described as " M. supra-clavic- 

 ularis prop r ins posterior." 



MORPHOLOGICAL SIGNIFICANCE 



To establish the morphological significance of the muscle in 

 question, the following facts deserve consideration : Gruber 

 (" Die Supernumeraren Brustmuskeln des Menschen," Mem. 

 de I'Acad. Imp. des Sciences des St. Petersbourg, VII Serie, 

 Tome III, No. 2, i860, pp. 3 and 6) describes 2. '' M. sterno- 

 clavicidaris superior, sen snpraclavicnlaris" as arising from the 

 manubrium sterni above and behind the origin of the sternal head 

 of the sterno-cleido-mastoid, from the margin of the clavicular 

 incisure and in some cases also from the margin of the semi- 

 lunar incisure. The muscle passes upward and outward, over 

 the sterno-clavicular capsule, behind the clavicular head of the 

 sterno-cleido-mastoid, to be inserted into the posterior surface 

 of the clavicle between " the beginning of the second and third 

 fifth of the bone." Gruber found this muscle five times in 100 

 subjects, four adult males and one boy. Twice it was bilateral, 

 twice present only on one side (right) and in one case only on the 

 left side. He figures an instance of the variation (loc. cit., Taf. 



I, fig. 4). 



A number of other anatomists have observed and described 

 the muscle, beginning with Haller, in 1766 (*' Elem. physioL," 

 Tome III, p. 46, Lausanne, 1766). Luschka (" Ein M. Su- 

 pra -clavicularis beim Menschen," Miiller's Archiv, 1856, p. 



