204 MR. R. H. BURNE ON THE 



(text-fig. 18, l.a.l}) (longitudinal) lobule. The lower lobe (test- 

 fig. 18, l.i.l.) is remarkably prolonged at its upper and outer angle, 

 forming a long finger-like cardiac process (text-fig. 18, l.i.l.a.) that 

 lies alongside the lower (transverse) lobule of the up]5er lobe 

 (text-fig. 18, l.cc.l.'^), bound to it by a fold of pleural membrane. 

 In the natural position these two elongated lobules embrace the 

 left side of the heart. 



The trachea, chief bronchial tubes, and pulmonary vessels call 

 for no particular notice, as they resemble closely those of the 

 Sheep. 



The Heart. 



The heart has a long narrow form, and measures 140 mm, in 

 total length from base to apex, and 95 mm. in breadth at the 

 upper part of the ventricles. The length of the ventiicular 

 portion is 120 mm. 



It is of the same type as that of other Ruminants. In 

 dissecting it, the musculi papillares of both atrio-ventricular 

 valves gave one the impression of being more than ordinarily 

 developed, particularly as regards the muscular swelling that 

 forms the foundation of those of the anterior cusp of the mitral 

 valve. The wall of the left ventricle seemed also to be thick for 

 a heai't of the size. 



The moderator band in the right ventricle is noticeably small. 

 The great arteries spiing from the arch of the aorta by a single 

 large innominate trunk, as in other narrow-chested Ungulates. 

 Between the aorta and pulmonary artery is a large vestige of the 

 ductus arteriosus. 



There is at the root of the aorta in Rviminants a very cha- 

 racteristic splinter of bone (os cordis) supporting the attach- 

 ment of one of the cusps of the aortic valve. In the Okapi 

 this bone is represented by a plate of cartilage, but whether its 

 unossified condition is a permanent character or is due to youth 

 it is difficult to say definitely, but it should be noted that in the 

 calf ossification* sets in almost immediately after birth, and that 

 in Antilocajjra'f the os cordis is permanently cartilaginous. 



The Thymus Body. 



The thymus is a relatively small triangular mass of tissue 

 attached by a fold of membrane to the antero-ventral surface of 

 the pericardium. It measures 64 mm. in length x 55 mm. in 

 breadth at its posterior end. 



The Stomacht (text-figs. 19, 20, 21, 22, 23). 



In its general form (text-fig. 19) the stomach of the Okapi 

 resembles that of the Giraffe and many Antelopes more nearly 



* Vaevst, " Herzknochen bei Wiederkauern," Deutscli. Zeitsclir. f . Tliiermedicin, 

 Bd. 30, 1888, p. 53. 



t Murie, Proc. Zool. Soc. 1870, p. 348. 

 j Gavrod, Proc. Zool. Soc. 1877, p. 5. 



