DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 95 



So far as could be ascertained by dissections and injections 

 no valves were found at the entrance of either the lateral or 

 cephalic trunks in the cephalic sinus, or at the opening of the 

 latter into the jugular vein, but as none of these orifices was 

 large a histological study might have revealed their presence. 

 Still, however, when the blood vessels were injected with a blue 

 mass, the cephalic lymphatic trunks were invariably filled from 

 either the lymphatic sinus or the inferior jugular connections 

 or through both, and when the blue was allowed partially to 

 solidify before the lateral trunk was injected with the yellow ; it 

 was found, upon dissection, that the yellow had forced back the 

 blue a short distance in both the jugular and in the cephalic 

 trunk, but none of it had reached the inferior jugular, showing 

 conclusively that if there were valves at the entrance of the 

 cephalic trunk opening into the cephalic sinus that after death, 

 at least, they are unable to repel an injecting mass, when only 

 a slight pressure is applied. 



It will be readily noted that the cephalic sinus of Polyodon 

 corresponds exactly in position to a siimilar reservoir described 

 by Vogt (i, pp. 137-8) in the salmon, but its shape and mode 

 of communications are very different. With the salmon this 

 sinus is said to empty into the ductus of Cuvier, and in addition 

 to receiving the lateral trunk it collects three mucous canals, as 

 they are called, from the head region. The first of these canals 

 is represented as arising at the origin of the temporal (pterotic) 

 crest from two branches coming from the facial region. The 

 second of these canals is portrayed (PL L, Fig. i, 63) as hav- 

 ing its source from six branches ; one large and one small vessel 

 coming from each of the first three branchial arches. The 

 smaller branch is said to have its origin from the filaments ; 

 while the larger branch is a more superficial trunk, that con- 

 tinues ventrad along the surface of the arch to anastomose with 

 the vein of Duvernoy (inferior jugular). The third canal comes 

 from a common reservoir situated near the fourth vertebra, 

 which is described as receiving a trunk from the fourth branchial 

 arch, and one from the median part of the body that also col- 

 lects the chylous duct. 



Hopkins' cephalic sinus in Ainia (8, p. 371 and Fig. 10, b) 

 Proc. Wash. Acad. Sci., July, 1907. 



