226 THE SALAMANDER 



already described. A small laryngeal v€\n can usually be found enter- 

 ing the vessel just before it merges into the ductus. 



(II) The V. lingualis (v.ling.) or Vena pharyngea? (Bethge). This 

 is essentially the vein of the tongue, emerging from that organ 

 between the anterior and posterior radials of the copula, and running 

 posteriorly along the mesial border of the first hypobranchial carti- 

 lage. At the point where the second hypobranchial cartilage unites 

 with the first branchial arch the vein loops back on itself a little so 

 as to allow it to stretch when the hyobranchial apparatus is pro- 

 tracted, while at this point also it receives a factor from the M. 

 subarcualis rectus I. The vein then leaves the cartilage and turns 

 somewhat mesially, passing dorsal to the arterial arches very close to 

 their origin from the truncus arteriosus. As the vessel passes over the 

 arteries it divides into two or more smaller veins which reunite to 

 form a single vessel on the posterior side of the pulmonary arch, thus 

 forming a closed venous loop. The reason for this is fairly obvious. 

 The space between the arterial arches and the pharynx is very re- 

 stricted, so that the vein must be subjected to considerable pressure 

 both from the blood in the arteries and from food passing down the 

 pharynx, and it is manifest that the blood would flow with more free- 

 dom under these circumstances if it were contained in several small 

 vessels instead of in one large one. At this point also several large 

 vessels from the ventral pharyngeal wall enter the vein, but the details 

 are particularly difficult to determine owing to the fact that the blood 

 or injection mass gets squeezed out of the veins by pressure from 

 the arteries. Emerging on the posterior side of the arterial arches 

 the vein turns sharply laterally and is soon joined by the thyroid 

 vein, and sometimes also by the common facial before entering the 

 ductus Cuvieri. 



Just at the point where the lingual vein turns laterally to meet the 

 thyroid vein it receives the efferent trunk from the central lymph 

 heart, constituting one of the most important connexions between 

 the lymphatic and venous systems. It is obviously this trunk which 

 Driiner refers to as 'Vena reuniens' (see also p. 260). 



(Ill) The V. thyroidea (v.th.) or V. lingualis (Bethge). The thy- 

 roid vein arises in the loose connective tissue between the hyobran- 

 chial muscles just anterior to the thyroid gland as the V. thyroidea 

 advehens (Druner) and passes posteriorly, ventral to the gland, re- 

 ceiving on its way numerous factors from the rich vascular network 

 of the gland itself. At the posterior margin of the thyroid gland a 

 cutaneous factor is received. This small vein arises in the skin in the 

 neighbourhood of the gular fold and passes to the region of the os 



