Circulatory System Special. 103 



The foramen ovale. 



In the Seals (Sectorialia) and other animals that live in water the 

 foramen ovale may remain open"^* for some time, but it is rare : in all 

 Cete, and in the Dugong (Sirenia), the fossa ovalis is closed. 

 Each precaval has a separate orifice into the auricle 



in many Insectivoray Cheiroptera, Rodentia, In-Enamellata, MarsU' 

 pialia, and Monotremata. 



Eustachian Valve. 



Sectorialia. The Eustachian valre is wanting in most species. 



Proloscidia. In the Elephant the Eustachian valve is large and 

 spirally twisted. 



Cete. The Eustachian valve is generally wanting. 



Right Auriculo- Ventricular Valve. 



Monotremata. In the Ornithorhyncus the right 'tricuspid' valve 

 consists of two membranous and two fleshy portions : the smallest of 

 the latter is situated near the origin of the pulmonary artery, 

 corresponds with the lesser fleshy valve in the heart of certain Birdsy 

 e.g. Pelican (Dysporo-morphse : Desmognathae), and is attached to 

 the whole of the side of the first or adjoining membranous portion r 

 the second fleshy portion answers to the larger muscular valve of 

 the Pelican. The two edges of the lower half of the second fleshy 

 portion of the valve in the Ornithorhyncus are free ; but those of 

 the upper half are attached to the two membranous portions of the 

 'tricuspid' valve ; the margin of the membranous part of the valve is 

 attached to the fixed wall of the ventricle by two small chordae 

 tendineae ; and the structure of the valve thus offers an interesting 

 transitional state letween that of the Mammal and that of the Bird. 

 Bone of the Heart. 



Artiodactyla. In most adult Huminantia and some Omnivora (^.y. 

 Hog), there is a bent bone at the base of the heart, on the septal 

 side of the origin of the aorta, and imbedded in the tendinous circle 

 which gives attachment to the muscular fibres of the ventricle. 



3. Arterial System. 



The Coronary Artery is said to be singlef in the Elephant. 



* Vander Hoeven, ii., 584. 

 t Camper. 



