DISSECTION OF THE UPPER EXTREMITY 



59 



(c) Its origin. 



(ca) Pars clavicularis. 



(cb) Pars sternocostalis. 



(cc) Pars abdominalis. 



(d) Its insertion. 



(e) Its innervation (Nn. thoracales anterior es]. 



(f) The bursa M. pectoralis majoris. 



Look up an article upon the torsion of the tendon of this muscle 

 by Dr. Warren Lewis, in the American Journal of Anatomy. 



FIG. 12. 



..Brachial arch 



Axillary arch 



The brachial and axillary arches. (From Poirier et Charpy, 

 Traite d'Anat. hum., Paris, 1901, 2 ed., p. 164, Fig. 126.) 



Axillary Fascia (Fascia axillaris). (Figs. 12 and 13.) 



Carefully remove the superficial fascia over the base of the 

 axillary fossa so as to expose the deep or axillary fascia. 

 Note- 



(a) An apparent oval opening between the concave aponeurotic bands; 

 the lower lateral concave band is the brachial arch (Armbogen of 

 Langer) ; the upper medial concave band is the axillary arch 

 (Achselbogen of Langer). If the dissection be made very care- 

 fully, a delicate, much-perforated membrane can be made out, ex- 

 tending from the brachial arch to the axillary arch, so that the 

 bundle of vessels and nerves seen through the oval opening is not 

 really subcutaneous. (Poirier.) Note the striking resemblance of 



