Geo. 8. Huntington 167 
d 
thoracic origin of the Pectoralis minor is retained, as in the Macaques 
(Pls. IV and V, Figs. 5 and 7). 
3. It will he noted, however, that in these latter forms the muscle has 
begun to shift its origin laterad, from the sternum to the adjacent 
costal cartilages. This is particularly the case in the specimen of 
Macacus melanotus, Gray—shown in Fig. 7, Pl. V (Columbia Univer- 
sity Museum, No. 1871). 
4. In some forms belonging to this intermediate type, the Pectoralis 
minor presents both the cephalic and lateral migration of the origin, 
which is carried to its full development in the secondary type found in 
Man and the Anthropoid Apes. 
Pl. V, Fig. 8, shows this character of the muscle in a specimen of 
Semnopithecus entellus (Columbia University Museum, No. 1251). 
III. SECONDARY TYPE. 
This is presented by the arrangement found in Man and in the closely 
corresponding disposition of the Pectoralis in the Anthropoid Apes. 
It is characterized by— 
1. Further differentiation of the individual muscles composing the 
group. 
2. Extension of the Pectoralis major to the clavicle and consequent 
relative reduction of the clavicular portion of the Deltoid. 
3. Migration cephalad of the insertion of Pectoralis minor from hu- 
merus to the ccracoid process of the pectoral girdle. 
!. Complete separation, consequent upon this shifting, of Pectoralis 
minor and abdominalis, at their insertion. 
5. The secondary assignment of the latter muscle, in its greatly re- 
duced form, as a component of the Pectoralis major, forming the abdomi- 
nal sip of the latter muscle, arising from the external oblique aponeu- 
rosis and inserting into the deep layer of the Pectoralis major tendon. 
6. Reduction of the Pectoralis minor and migration laterad of the 
origin of this muscle from sternum to the ribs, obtaining the conse- 
quent digitate attachment to a varying number of the upper ribs, below 
the first. 
%. The freeing of the sternum by the lateral recession of the minor 
affords the increased area of sternal attachment for the Pectoralis major, 
which muscle, in addition, occupies in its deeper portion some points of 
attachment to the costal cartilages. 
8. Reduction of the thoracic panniculus in the axillary region and 
the disappearance, in Man and the Anthropoid Apes, of the axillary 
arch as a normal muscular integer, while the same is still observed as 
a frequent individual variation. 
