390 CETACEA. 



sections of vascular channels (?;.)* There are, however, others, chiefly round openings, 

 of much smaller calibre and with remarkably thick walls as compared with their 

 narrowed central channels. Besides these (best shown in fig. 4) are what may 

 correspond partly to oblique or in some cases to the longitudinal sectional view of 

 capacious blood-vessels, which apparently have a great number of tributaries piercing 

 their fibrous walls (fig. 4, Iv.). 



Seart and blood-vessels. ^-^-The heart of Orcella is of considerable size, but not 

 so large proportionally to the animal as is the heart of Flatanista, neither is it so 

 markedly bifurcated at the apex, nor are the auricles so loculated as in the latter 

 dolphin. The ventricular septum passes downwards slightly to the right side and 

 the base of the organ is flattened, but its right half is lower and its right ventricle 

 and auricle smaller than those of the left side ; the former cavity is larger, but 

 much narrower than its fellow. The left auricle, when the heart is distended, is 

 closely applied over its base, and the right margin of this auricle touches the pul- 

 monary artery ; but the right auricle under similar circumstances projects upwards 

 from the base of its ventricle, anteriorly exposing a considerable portion of it. The 

 heart measures in the adult 5 inches across the base of the ventricles, and 3"*50 

 from the origin of the pulmonary artery to the apex of the left ventricle ; antero- 

 posteriorly it is 3 inches through the thickest portion of the right ventricle, and 

 across the auricles about 5-75 inches. (See Plate XXIX, fig. 2.) 



At the point where the pulmonary artery has the pericardium reflected on to it, 

 and occupying about the position of the ductus arteriosus, two pits occur, separated 

 from each other by an interval of 0'25 inch. These are about 0'25 inch in 

 diameter and the same in breadth, and the one to the left is a blind sac, defined on 

 each side by tendinous or pillar-like folds of the pericardium prolonged on to the 

 pulmonary artery. The other is protected at its upper border by a cord-like band 

 that stretches across it transversely. To the left side it gives off a thinner and 

 fibrous cord directed obliquely forwards. At the bottom of the pit there is a deep 

 recess that admits a large probe, and passes dorsally obliquely outwards. Unfor- 

 tunately the parts at the side of the left bronchus where the probe appears have 

 been cut across, but the probe is seen to lie in a well-defined tube. There seems 

 little doubt but that these invaginations of the pericardium mark the remains 

 of the ductus arteriosus. 



In the cavities and valves of the heart nothing specially worthy of note 

 occurs. 



I had the opportunity of examining the distribution of the vascular trunks and 

 branches which spring from the aorta both in an adult and in a fcetal specimen. 

 A sketch of the former is given in Plate XXIX, fi^. 2, in which figure, the 

 numerous cervical and upper pectoral glands in relation with the vessels are also 

 given. 



^ Besides Hunter, Carte and Macalister, Murie, &c., Turner in his " Account of the Great Tinner Whale," 

 I. c, p. 227, gives a good description of the circulatory organs. 



