470 SCHULTE, SEI WHALE. 



At the level of the hypogastric artery the postcava' receives on each side a large iliac vein, 

 beyond which they are continued into the caudal veins which soon become plexiform. While 

 draining into both postcavse the connection is distinctly larger on the right side. Between the 

 origins of the hypogastric arteries a small ventral anastomotic branch ascends from the left iliac 

 to the right postcava. This is connected on each side by a slender vessel with both caudal 

 veins. In anastomoses placed ventral to the arteries we have the retention of an embryonic 

 condition common to Monotremes, Marsupials and Placentals, which is highly developed in the 

 first, a frequent variant in the second, and is regularly replaced by a dorsal anastomosis in the 

 adults of the third. The passage of the anastomosis dorsal to the aorta at this point is also 

 common to the three subclasses, and is frequently of high development among the Marsupials, 

 although they show much individual variation in this arrangement. 



Of the several axial embryonic venous channels which may form the postrenal segment 

 of the postcava, it is practically certain that it is the supracardinal of Huntington and McClure 

 which has here persisted, for the ureter is free of the postcava and does not twist around it as 

 is the case with the retention of the postcardinal, while the possibility of the existence and reten- 

 tion of the cardinal collateral of McClure seems excluded by the lateral position of the post- 

 cava beside the aorta. The existence of this vessel, in the present state of our knowledge, can 

 hardly be asserted except of Marsupials and Tragulus, and its retention gives rise to a cava of 

 preaortic position. We may then recognize in the postcaval system of this fcetus distad of the 

 liver, a subcardinal portion comprising the subhepatic trunk and the debouchment of the renal 

 veins, and a supracardinal represented by the double veins and the anastomosis dorsal to the 

 aorta. 



In the course of the postcava? numerous small tributaries enter laterally from the plexus 

 upon the hypaxial muscle and from the substance of the muscle itself. The sex veins failed to 

 be injected and I was unable to recognize them with any certainty. A rather large vein near 

 the middle of the cava was directed laterad towards the ovary, but I could not determine its 

 drainage area. 



The postcava of this fcetus differs in one respect from that described and figured by Daudt l 

 in B. musculus. In this specimen the left postcava was carried up to the renal level and its 

 contents gained access to the single subhepatic cava by means of the subcardinal anastomosis, 

 which is the typical placental arrangement in cases of double postcava. In his specimen dorsal 

 anastomoses are hot recorded and the cavo-spinal anastomosis is represented by several vessels. 



CERVICO-BRACHIAL PLEXUS. 



Cervical plexus. The ventral divisions of the first four cervical nerves conform to the 

 usual mammalian type as far as their muscular branches and communications are concerned; 

 cutaneous branches I was unable to examine. The first and second communicate ventrad of the 

 transverse process of the atlas. From this loop the decendens cervicalis is given off to the hypo- 

 glossal. The communicans arising from the second and third, crosses the carotid and joins the 

 decendens shortly after it parts company with the hypoglossal. Thus a very short anser is 

 formed, from which a trunk descends in the carotid sheath and resolves itself into branches for 



Daudt, W., op. cit., pi. vii, fig. 7. 



