THE VASCULAR SYSTEM 201 



optic peduncle and is distributed to the MM. rectus superior, 

 anterior, and inferior. 



(ii) R. ophthalmicus superior posterior (a.oph.s.p.). This branch 

 passes directly dorsalwards and is distributed to the upper eyelid and 

 the skin above the skull in the posterior orbital region, as well as to 

 the tissue surrounding the eye itself. It fuses with the superior 

 orbital branch of the A. petrosa lateralis. 



(iii) R. ophthalmicus superior anterior (a.oph.s.a.). The third ter- 

 minal branch of the ophthalmic artery passes dorsalwards together 

 with the previous one and is distributed to the anterior portion of the 

 upper eyelid and the skin of the head, as well as to the general tissues 

 around the eye. It passes round the orbit along the dorsal border of 

 the orbito-sphenoid and ultimately fuses with a branch of the palato- 

 nasal artery and enters the nasal capsule. In addition it supplies both 

 the oblique muscles of the eye. 



5. Branches of the Systemic Arch (PL XIV). 



The systemic arch runs in company with the carotid arch in an 

 antero-dorsal direction to the occipital region of the skull, and then 

 bends round mesially to unite with its fellow from the other side in 

 the middle line to form the dorsal aorta (q.v.). The vessels given 

 off from this arch are four in number. 



A. A cutaneous branch passes dorso-laterally between the two por- 

 tions of the M. cephalo-dorso-subpharyngeus to which it gives a 

 small branch. It is distributed to the thymus and paratoid glands. 

 This vessel arises very close indeed to the point where the 'third' 

 arch enters the systemic, and in one specimen it appeared to be 

 actually continuous with this vessel. In view of the fact that it 

 divides the pharyngeal constrictor into two sections dorsally, just as 

 the 'third' arch does ventrally, it would appear to be actually the 

 peripheral continuation of this arch, but only an investigation of the 

 conditions prevailing at the period of metamorphosis would settle 

 this point. 



B. A. pharyngea ascendens (Osawa) (a.ph.asc). 



A. maxillaris externa Bethge (1898). 



A. mandibulo-jugularls Druner (1904). 



This artery arises laterally close to the previous one at about the level 

 of the posterior end of the ceratohyal and passes antero-laterally, 

 mesial to the M. depressor mandibulae, to the posterior edge of the 

 squamosal. It has six branches: 



(i) RR. cutanei dorsales (Osawa) of which one passes lateralwards 



