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regards as a continuation forward of the m. serratus anterior. I have 

 studied the fascia in this region in forty-five subjects, in the Ana- 

 tomical Laboratory of the university of Chicago, and so far as the 

 fascia is concerned, my observations have been to a large extent con- 

 firmatory of those which he reports. 



In this region there appears in my dissections a fan-shaped sheet 

 of fascia covering the upper two or three intercostal spaces, the fibers 

 of which run downward and lateralward over those of the subjacent 

 mm. intercostales externi. This fascia has usually a superior attach- 

 ment to the anterior surface of the first rib, from the costal cartilage 

 to the point of insertion of the m. scalenus medius. It extends thence 

 downward and dorsalward, the medial fibers almost vertically to the 

 second or third rib, the lateral fibers obliquely to the third and 

 second rib, and to that part of the m. serratus anterior arising from 

 them. The anterior and medial part of this fascia is weak, but lateral- 

 ward it becomes thicker and in its upper and lateral part it is usually 

 quite strong. 



While the above is the common disposition of the fascia, some 

 variations from it were observed. Occasionally the continuity of some 

 fibers with the second part of the m. serratus anterior is well marked, 

 and in one subject a portion of the membrane was formed partly of 

 muscle fibers continuous with those of the m. serratus anterior, 

 constituting thus a prolongation of that muscle as far as the first 

 costal cartilage. In seventeen others of the forty-five subjects examined, 

 while the fascia did not contain any muscle fibers, there existed a 

 thickening in its upper and lateral part forming a powerful ligamentous 

 band, which passed from the anterior border of the muscle forward 

 and upward to the fii'st costal cartilage. This ligamentous band is 

 identical with the structure commonly described as a fibrous arch 

 between the first and second ribs, from which part of the m. serratus 

 anterior is said to arise. In two subjects the fascia presented inter- 

 esting relations with the m. scalenus medius. In these the m. scalenus 

 medius was prolonged down to the second rib, in one case lying super- 

 ficial to the m. serratus anterior and to the fascia, and in the other, 

 lying internal to the m. serratus anterior, between it and the m. inter- 

 costalis externus. 



The entire fascia appears to be derived from the m. serratus 

 anterior and to represent a prolongation of this muscle forward and 

 upward over the anterior ends of the first two costal arches and inter- 

 costal spaces. It appears necessary to adopt this view of the nature 

 and origin of this fascia for three reasons : first, the fibers of the fascia 



