HEART, CIRCULATION, AND BLOOD 



159 



whole problem is still far froin being solved, we may safely state that, in 

 this respect too, the Cetacean heart is not radically different from that of 

 other mammals. 



Everyone who has seen the flensing of a whale, particularly of a Sperm 

 Whale, is struck by the quantities of blood that keep pouring from the 

 carcass. However, calculations have shown that the ratio of blood to body 

 weight is only 6 -5 per cent in Blue Whales and 5 -5 per cent in Belugas, the 

 corresponding figures being 4-8 per cent in rabbits, 5 per cent in rats, 

 6-6 per cent in horses and 8*i per cent in sheep. Clearly, this is another 

 respect in which Cetaceans are very much like other mammals. 



Some hint about the strength of an animal's heart can be gleaned from 

 its shape. In porpoises, the heart is a little longer than it is bi'oad, in most 

 other toothed whales length and breadth are approximately equal, while 

 in Mysticetes and Sperm Whales the breadth exceeds the length. The 

 Biscayan Right Whale has the broadest heart of all. All these peculiar 

 shapes, which are characteristically different from the more elongated 

 shapes of the hearts of most mammals (Fig. 90), are undoubtedly the result 

 of the peculiar shape of the Cetacean thorax. In the last chapter, we saw 

 that because of the dorsal position of the lungs, the peculiar angle of the 

 diaphragin and the barrel-shape of the thorax itself, the available space 

 for the organs in the ventral part of the thorax has become broader and 



Figure go. Left views of the heart of (a) a horse, (b) a porpoise and (c) a Fin Whale to 

 show differences in shape. A = aorta; P = pulmonary artery. Note the ductus arteriosus 

 between the two arteries in (a) and {b}, where it has become fused into a ligament. The hearts 



are not drawn to scale. 



