CHAP. IV] THE GENERAL ANATOMY OF GORILLA 187 



Gorilla is in a phase of evolution which is transitional and inter- 

 mediate between Hominidae and the other Simiidae 1 . 



G. Vascular System. The heart closely resembles the human 

 organ : in respect of length it bears to the stature a ratio slightly 

 higher than is the case in Man. In position it is turned as much 

 to the left side of the thorax as is the human heart 2 , and thus the 

 Gorilla stands in strong contrast with the Cercopithecidae. 



The arrangement of the great arteries springing from the arch 

 of the aorta is identical with that of Man in 89 ^ of examples. 

 The foregoing characters bear some relation to the increased width 

 of the thorax found in the erect and semi-erect Primates. A few 

 notes on the peripheral vessels will now be added. 



The axillary artery resembles that of Man in its upper portion 3 , 

 but in the lower part, the presence of a common trunk of origin 

 for the circumflex arteries of the scapula and humerus (anterior 

 and posterior circumflex arteries and the " dorsalis scapulae "), 

 constitutes a distinct retention of the conditions met with in the 

 Cercopithecidae. 



The A. brachialis lies superficially to the median nerve. It is 

 thus an A. brachialis superficialis (not commonly retained in Man) 

 and it gives off the radial and ulnar arteries. The ulnar artery 

 asserts itself more distinctly than in the Cercopithecidae as a 

 channel of supply to the palmar aspect of the hand. Its super- 

 ficial division supplies the little finger and the ulnar aspect of the 

 ring finger, the superficial palmar arch being as yet undeveloped. 

 The deep division joins the radial artery to form a distinct "deep" 

 arch, to which the radial contribution is the greater. 



The striking feature of the arteries in the lower limb is the 

 retention of the A. saphena. This vessel may be regarded as an 

 archaic possession, occurring occasionally in Man as an anomaly. 

 The plantar arteries resemble those in the human foot, save that 

 they are relatively smaller, the dorsal contribution to the deep 



1 The Mm. contrahentes are rare in Gorilla (Keith, Proc. Zool. Soc. 1899, 

 March 7). 



2 Eisler, Das Geftiss- urul periphere Nervensystem des Gorilla ; Ruge, Morpho- 

 logisches Jahrbuch, Band xix, with illustrations. 



3 Manners Smith, J. A. P., Vols, xliv, xlv, xlvi. I have checked the descriptions 

 by reference to dissections in the Cambridge Museum. 



