040 mil. c. II. o'bonoouue on tue 



IV. Two longer ciliary branches (Aa. ciliares posticfe longje, 

 llathke), one of wliicli runs forward on the inner side of the eye 

 and the other outward on its liinder side. 



V. A Retinal Artery (Art. centralis retinie, Rathke) which 

 enters the eyeball with the optic nerve and spreads out over the 

 retina. 



(B) Veins. 



The veins of the head of Tropido7iott(,s natrix have recently 

 been described in great detail by Bruner (12), who also describes 

 a muscular mechanism in the head whereby the blood-pressure in 

 it-) veins and sinuses may be corsiderably increased. It is not 

 possible by ordinarj' dissection to make out all the small vessels 

 given by that author, and, as my own results agree closely with 

 his, it will only be necessary, for the sake of completeness, to give 

 a brief description of the cephalic veins. 



The Mandihular Vein (V. inframaxillaris, Schlemm ; "V. mandi- 

 bularis, Bruner) arises from a small sinus at the fi,nterior end of 

 the lower jaw and runs backwards close to and on the outer side of 

 the external carotid arter}^. On its way it receives veins from the 

 trachea, tongue-sheath, muscles of the floor of the mouth, and 

 the pharynx. It runs into the maxillary vein immediately before 

 the latter joins with the latei'al cephalic vein to form the common 

 jugular vein. The bases of the mandibular, maxillary, and lateral 

 cephalic veins and the anterior end of the common jugular vein 

 are surrounded by constrictor muscles whose morphology and 

 function are described by Bruner (loc. cit.). 



The Maxillary Vein (Y. palatina, Schlemm ; V. maxillaris, 

 Bruner) also commences in a small sinus which is situated just 

 behind the premaxilla. This sinus has a double anastomosis with 

 the similar one on the other side. I*rom this point it runs back- 

 wards beneath the nasal cavity along the floor of the orbit and 

 then above the palate to join the mandibular vein at the angle of 

 the lower jaw. During its course it receives : — 



I. The Rostral Vein (Y. rostralis, Bruner), which enters at the 

 level of the anterior anastomosis and brings the blood from a 

 venous network at the front end of the snout. It also receives 

 nasal veins (Y. nasales externse, dorsalis, and ventralis, Bruner) 

 from the nasal gland. 



II. The Stibnasal Vein (Sinus subnasalis, Bruner), which enters 

 at the level of the posterior anastomosis. It drains a somewhat 

 complex system of subnasal sinuses, which anastomose with one 

 another at the posterior end of the nasal cavity and which receive 

 also the palato-pterygoid vein. 



The Palato-2}terygoid Vein (Sinus palato-pterygoideus, Bruner) 

 runs from near the anterior to near the posterior end of 

 the skull on the inner side of the palatine and pterygoid 

 bones, and flows into thfe anastomosis between the sub- 

 nasal sinuses. 



