765 



Specimen A. Rana tcwporaria (see figure 5«). 

 In this specimen the sub-clavian, innominate, and external jugular 

 veins of the right side join together in the normal way, but instead of 

 forming a precaval vein they end blindly. There is however a dilated 

 and somewhat varicose vein forming an anastomosis between the external 

 jugulars of the two sides. It runs in the form of a double arch from 

 the confluence of the lingual and mandibular veins of the right side to 

 the similar confluence on the left and it is evident from its size and 

 position that it conveyed the blood normally taken to the sinus venosus 



KJ. 



Fig. 5. Diagram of Venous Systems with Right Precaval Absent. A, Specimen A; 

 B, Specimen B; An, Anastomosis; Br, Bracihal; E.J, External Jugular: I. Inno- 

 minate; I.J, Internal Jugular; L, Lingual; L.A, Left Precaval; M, Mandibular; 

 M.C, Musculo-cutaneous; S.C, Sub Clavian; S.S, Sub Scapular. 



by the right precaval, to the left external jugular. The varicose appear- 

 ance of this anastomosis suggests that the blood did not find an easy 

 passage in this direction. As a result of this absence of a precaval 

 vein there are only two cavai veins opening into the sinus venosus. 



Specimen B. Rana temporaria (see figure hh). 

 Here again we have an entire absence of a right precaval vein and 

 consequently only two veins opening into the sinus venosus and indeed 



