THE VASCULAR SYSTEM 195 



with the respiratory function of the vessels he is describing than with 

 their exact anatomical relations. He improves on existing accounts 

 by giving some description of the vessels of the head region, but in 

 this he is not quite accurate. He figures the lingual vein as passing 

 ventral to the arterial arches and says that it breaks up into a 'Rete 

 mirabile' in the region of these vessels. 



The only vessel that can be identified with the vein he describes 

 is the V. thyroidea^ while the 'Rete mirabile' must be the thyroid 

 gland itself. It is astonishing that he should have fallen into this 

 error, as the development of the thyroid gland had been well de- 

 scribed only four years previously by Maurer, but his figure allows no 

 other explanation, since the thyroid vein is the only vein in that 

 region passing ventral to the aortae. Bethge accurately figures and 

 describes the proximal portion of the true lingual vein — which 

 passes dorsal to the arterial arches — as the V. pharyngea. 



Only two more authors need be noted here, namely, Choron- 

 shitsky (1900) who gives a good account of the development of the 

 mesenteric veins and of the hepatic portal system, and Konigstein 

 (1903) who describes the pulmonary and related arteries. 



The vessels of the brain were first described by Scholb in 1882. 

 His figures are very beautiful but not quite accurate, particularly 

 in respect of the veins, and his work was amended later by Rex 

 (1893). 



2. General Features. 



The condition of the blood-vascular system in the Salamander is 

 extremely interesting, and it is surprising that no really adequate 

 account of it exists, for we have in one and the same animal what 

 amounts to two systems of blood-vessels — that of the fish and of the 

 land vertebrate, and particularly is this so in the case of the venous 

 system. The Salamander thus forms a nearly perfect transitional 

 type, being in this respect much less specialized than the Frog. 



The chief features of interest may be tabulated thus: 



Arterial System. 



(i) Persistence normally of four arterial arches in the adult, 

 (ii) Occurrence of a perforate ductus Botalli between the pul- 

 monary and systemic arches, 

 (iii) Limitation of the area served by the carotid arch, 

 (iv) Distribution of a branch of the systemic arch to the palate, 

 (v) Distribution of branches of the pulmonary arch to the 

 oesophagus and pharynx. 



