184 MR. F. E. BEDDARD ON THE [Feb. 19^ 



Vena hemiazygos miinclet direkt oder indirekt in die Vorkammev."^ 

 But, as I shall show, this is not quite imiversal. 



Since the system of azygos veins is as perfect in the Gnu, 

 Connochmtes gnu, as in any other XJngulata, and more elaborately 

 developed than in many, I shall commence with a description of 

 those veins in this Antelope. The anterior vena cava receives a 

 right and a left azygos vein which enter it very nearly, if not 

 exactly, opposite to each other. Of these two the right is rather 

 longer than the left. This I'ight azygos receives five branches, of 

 which the most anterior is composed of affluents from two ribs. 

 It is evident therefore that the right azygos does not reach back 

 nearly as far as the diaphragm. The left vein is composed of 

 only four intercostal branches. The blood from the ribs lying 

 behind these four are connected, however, into another lon- 

 gitudinal trunk lying on the left side. Seven or eight of these 

 branches coming from as many intercostal spaces combine to 

 form a vein running in the same straight line as the left azj^gos, 

 but not joining it anteinorly. The vein, in fact, opens inde- 

 pendently into the right auricle, as previous observers have noted 

 for other Ungulates. 



It is not a little remarkable that the other species of Gnu, 

 viz. ConnocJuetes iaurimts, which I have also dissected, shows 

 difierences in respect of these veins from C onnochcetes gnu. On 

 the right side the azygos is a trifle smaller and collects blood only 

 from four intercostal spaces. On the left side the azygos is very 

 much longer, with seven or eight affliients. It enters the vena 

 cava superior as in Marsupials ifec, which possess two azygos veins. 

 I did not detect any branch putting this vein into direct com- 

 miuiication with the right auricle, such as occurs in Connochcetes 

 gmi and in some other forms which I shall deal with immediately. 

 An intermediate condition is offered by another Antelope, Buhalis 

 caaina. In this animal the right azygos is composed of five 

 affluents. On the left side we have both the anterior and the 

 posterior vein of Connochcetes gmt, and, as in that animal, the 

 latter communication with the auricle direct. But a slender twig 

 connects the two veins, which are thus a continuous vessel as in 

 Connochcetes taurinus. 



The azygos veins of Rhaphicerus melanotis present the usual 

 Antilopine characters ; but there are differences of detail from 

 those of some other forms. On the right side, the internal 

 mammary vein is followed in passing towards the heart by a 

 superior intercostal which divides into two branches, each of which 

 supplies the first or the second intercostal space. Behind this 

 arises the right azygos, which is composed of three affluents ; the 

 first lies in the intercostal space 2/3, the others in 3/4 and 4/5. 

 Thus the intercostal space 2/3 has two veins. On the left side 

 there is a superior intercostal opening exactly opposite to the right- 

 hand vein ; but it is a larger vessel though it only draws blood from 

 two intercostal spaces. The left azygos, as in allied forms, is well 

 developed and enters the heart in common with the vena cava 



