Page:The American Cyclopædia (1879) Volume VI.djvu/199

DOLPHIN 191 verse being about as long as the spinous pro- cesses; the lumbar vertebrae are 18, with very long transverse and spinous processes ; a sacral vertebra can hardly be said to exist, as the pelvis consists of a rudimentary bone on each side suspended in the muscles ; the caudal ver- tebra? are about 28, gradually decreasing in size, the transverse processes disappearing about the 16th, and the spinous about the 20th ; exclusive of the cervicals, there are about 60 vertebra in all ; the Y-shaped bones on the under surface of the bodies begin about the sixth caudal. The breast bone is composed of three bones, the first very wide, grooved in front, and usually pierced with a hole; the shoulder blade is fan-shaped, slightly concave ; the clavicle is absent ; the pectoral fin is com- posed of a very short humerus, with a large upper tuberosity, its lower extremity compress- ed antero-posteriorly, and uniting by a carti- laginous articulation on an irregular line with the bones of the forearm ; the latter are almost rectangular, short and flat, the radius in front and the widest; the bones of the wrist, six or seven in number in two rows, form a flat pave- ment-like surface united by cartilage to the radius and ulna; there is a mere vestige of thumb, according to Cuvier, the index finger being the longest and having nine articulations with its metacarpal bone and phalanges, the third with seven, the fourth with four, and the fifth a mere tubercle. This anatomical de- scription will answer generally for dolphins and porpoises, and the allied genera. Dol- phins are among the swiftest of cetaceans, and their speed is owing to the strokes of the pow- erful tail; the pectoral fins serve merely to balance and guide the body, and to carry the young. The eye and ear are of the mamma- lian type; the nasal passages seem destined only for the expulsion of water from the mouth and for the introduction of air into the lungs, and are generally considered as not endowed with an average sense of smell ; the taste must be very imperfect, and the sensibility of the naked skin low. The teeth are formed only for seizing and retaining prey, which is swal- lowed whole. Authors differ as to the stom- ach, some making it single, but most divi- ding it into three, four, or five compartments more or less complicated ; the intestine is sim- ple, 10 or 11 times as long as the body, and gradually diminishing from the stomach to the anus. The dolphin is not a fish, but an air- breathing mammal, warm-blooded, viviparous, and suckling _ its young. Though shaped like fishes, inhabiting the water exclusively, and moving in the same manner with them, it must come to the surface by means of its horizontal tail, and take in air through the single spiracle on the top of the head, which it can do when the mouth is full of water by means of the upward prolongation of the larynx into the nasal pas- sages, and the shutting off of its cavity by mus- cular action from the mouth and oesophagus ; the external opening of the spiracle is guarded 269 VOL. vi. 13 by a valve, which prevents the entrance of water when the animal plunges beneath the surface. The water taken into the mouth with the food can be made to pass out in a jet from the spiracle, by the closing of the phar- ynx, and the forcing of the liquid into the nose through the passage in which the larynx is elevated during respiration. Under the skin, in front of the nostrils, are two large cavi- ties covered with muscles ; into these the water is sent, and remains until the animal chooses to eject it ; then closing a valve at their entrance, the water is sent forth by the contraction of the muscles. The dolphin family make a feeble moaning or plaintive noise, which has often been noticed when they have been stranded alive. The circulation is carried on as in other mammals ; only, in order to enable them better to remain under water, there is a plexiform arrangement of the arteries within the chest and near the spine, which serve as reservoirs of pure blood during immersion ; these do not communicate directly with veins, and their contents can be taken into the circulation as circumstances require. The reproductive or- gans are the same as in other mammals, and their functions are similarly performed ; the testes are within the abdomen ; the prostate gland is large, but the seminal vesicles are ab- sent; the mammas are two, with the nipples concealed in a fold of skin, except during lac- tation, when they protrude on each side of the genital opening. The kidneys are made up of many small glands united. The brain is very wide, the hemispheres however covering only a portion of the cerebellum ; the convolu- tions are numerous and complicated, but nar- row ; the olfactory lobes seem to be wanting ; the cerebellum is well developed, with distinct median and lateral lobes. This great cerebral development affords some ground for the an- cient belief in the superior intelligence of the dolphin. The history of this animal, sacred to Apollo, though encumbered with fabulous and superstitious accounts, doubtless contains much truth which whale-hunting moderns have not cared to examine. As the dolphin family till recently included all ordinary ceta- ceans with small heads, the divisions which have since been made are very numerous, and no system of classification as yet offered can be called natural. Such only, therefore, as would not come more properly under other popular titles will be briefly alluded to. At the head of the list is the common dolphin (D. delphis, Linn.) ; this, from the shape of the beak, is vulgarly called the "goose of the sea;" it was the hieros ichtJiys (sacred fish) of the ancients, the favorite of Apollo (whose most famous oracle bore its name), and the supposed bene- factor of man ; it is seen on very ancient coins and medals, and formed a conspicuous object on the coat of arms of the princes of France ; from it was named the province of Dauphiny, which gave the title to the heir apparent to the French throne. It attains a length of