00 HUNTINGTON 



Brown, the M. stcrno-choiidro-scapidans, corresponding to a 

 muscle normally encountered in many mammalia, is found not 

 very uncommonly, extending between manubrium of the sternum, 

 or the first rib or its cartilage and the upper border of the scapula, 

 usually near the suprascapular notch or the base of the cora- 

 coid process. This aberrant muscle passes behind the normal 

 subclavius, when that muscle is present, while in other cases the 

 typical subclavius is absent and is replaced by the abnormal 

 muscle. 



Considering the relationship of the subclavius insertion to the 

 coraco-clavicular ligaments and to the coracoid process of the 

 scapula it is not a very farfetched view to regard the normal 

 human subclavius muscle as a derivative from the mammalian 

 sterno-chondro-scapular sheet, which has lost its scapular at- 

 tachment, and receded to the inferior surface of the clavicle, 

 while its original distal portion, metamorphosed into fibrous 

 tissue, remains as the coraco-clavicular ligaments. 



Again the whole group of retro-clavicular supernumerary 

 muscles are properly to be referred to the same mammalian 

 sterno-chondro-scapular muscular sheet of which they represent 

 myotypical rev^ersions in the sense defined by me on a previous 

 occasion. I think that Testut (loc. cit., p. 55), in quoting the 

 only two previously recorded cases of retro-clavicular supernu- 

 merary muscles (Weber's and Tait's), strikes the correct key- 

 note of their morphological significance, when he says, regard- 

 ing Tait's case : "If this muscle had had a few centimeters 

 greater length it would have become attached to the upper 

 border of the scapula, and we would have changed its name and 

 place in the classification ; it would have been a sterno chondro- 

 scapularis." 



REPORTED INSTANCES OF UNION OF THE 



STERNO-CLEIDO-MASTOID AND 



TRAPEZIUS 



In conclusion it may be well to consider that some reported 

 instances of more or less complete union of the sterno-cleido- 



