84 THE GENERAL ANATOMY OF THE LEMUROIDEA [SECT. A 



All the foregoing characters are primitive, and correlated 

 with the narrowness of the proximal portion of the thoracic 

 cavity. 



The position of the carotid foramen and the direction of the 

 carotid canal in the skull shew that in Lemurs as in the lower 

 Apes, the artery enters the skull obliquely, i.e. with an angle 

 widely open to the ventral aspect. The entrance to the carotid 

 canal is close to the medial side of the foramen stylo-mastoideum. 

 Winge describes the internal carotid artery as dividing in its 

 course through the canal, or rather as giving off a stapedial 

 branch from which the middle meningeal artery is ultimately 

 derived. 



In the Lemurs of the family Lorisinae, the brachial and 

 femoral arteries divide suddenly into many parallel minute 

 branches constituting a form of " rete mirabile." The explanation 

 of this remarkable condition (apparently subversive of the expecta- 

 tions based on morphological principles) has yet to be provided. 

 That the basis is physiological can scarcely be in doubt. Moreover 

 the Lorisinae have a curious reptilian slowness of movement. 

 Yet the presence of similar arterial subdivisions in the limbs of 

 the essentially active Tarsius (as described by Burmeister, v. infra, 

 p. Ill), shews that the explanation must be sought in some other 

 connection. 



The axillary artery is characterized by a tendency to the 

 development of a subscapular offshoot whence four vessels arise, 

 viz. the Aa. circumflexa humeri, circumflexa scapulae, thoraco- 

 dorsalis and subscapularis. The brachial vessel is of the 

 " superficial " type {i.e. it passes downwards superficially to the 

 median nerve) and it sends an offshoot to pass with the median 

 nerve through the entepicondylar foramen. In the Lemuroidea, 

 first among the lower quadrupedal mammals, the ulnar artery 

 begins to assert itself as a contributor to the palmar arterial 

 arches. 



In the lower limb, the common femoral trunk often gives off 

 the A. circumflexa lateralis. An A. saphena, of the type so 

 distinctive of the higher Primates, is not usual. In the foot, 

 the medial plantar artery is of large size and extensive distribution. 

 The lateral plantar artery is not found. 



