HEART OF THE DUGONO. 



709 



poured through the vence cavce into the right or pulmonic auricle ; and 

 hence it passes into the right ventricle (fig. 403, b), to be again re- 

 turned through the pulmonary artery to the lungs, thus completing the 

 circulation. 



(2335.) But although the general arrangement of the circulatory and 

 respiratory organs in all Mammals thus in every respect resembles that 

 which exists in the human body, there are of necessity variations in 

 the distribution of certain parts of the sanguiferous system, adapted to 

 the peculiarities of organization presented by the different orders and 

 even families of this great class, which must not be wholly passed over 

 in silence. 



Fig. 403. 



d 



(2336.) IntheCETACEA, 

 for instance, many inter- 

 esting circumstances are 

 observable in the arrange- 

 ment of th e vas cular system . 



(2337.) In the herbi- 

 vorous genera, as for ex- 

 ample in the Dugong, the 

 two sides of the heart are 

 separated to a considerable 

 extent by a deep fissure 

 (fig. 403, a, b), so that the 

 pulmonary and systemic 

 hearts are much more evi- 

 dently distinct viscera than 

 they appear to be in the 

 quadrupedal forms ; never- 

 theless in the Whalebone 

 and Spermaceti Whales the 



heart assumes the usual appearance, and is only remarkable for its 

 amazing size ; this, indeed, may well have attracted the notice of 

 Hunter* while investigating such gigantic beings. " In our examina- 

 tion of particular parts," says that eminent anatomist, " the size of 

 which is generally regulated by that of the whole animal, if we have 

 only been accustomed to see them in those which are small or middle- 

 sized, we behold them with astonishment in animals so far exceeding 

 the common bulk as the Whale. Thus the heart and aorta of the Sper- 

 maceti Whale appeared prodigious, being too large to be contained in a 

 wide tub, the aorta measuring a foot in diameter. When we consider 

 these as applied to the circulation, and figure to ourselves that probably 

 ten or fifteen gallons of blood are thrown out at one stroke, and moved 

 with an immense velocity through a tube of a foot in diameter, the 

 whole idea fills the mind with wonder." 



* The Animal (Economy, by J. Hunter, with Notes by Professor Owen, p. 366. 



Heart of the Dugong. 



