194 



THE QUARTERLY REVIEW OF BIOLOGY 



thai, 1891). In the typical mammalian 

 hand the number of phalanges in each 

 finger does not exceed three, whereas as 

 many as seventeen have been observed 

 in foetuses of Globkepbala. Whalebone 

 whales apparently lack the thumb, but 

 it is present in the toothed whales. The 

 chief function of the flippers is to enable 

 the whale to descend or ascend, or to 

 turn sideways. They are used mainly 

 for steering and balancing, and have lost 

 their former rowing function. The pro- 

 pelling mechanism of a whale is centered 

 in the powerful flukes at the end of the 

 tail, and the muscles and tendons that 

 control these organs of propulsion act as 

 levers, which pull them in an up and down 

 direction. The greatest velocity is pro- 

 duced by alternate upward and downward 

 strokes of the flukes. When proceeding 

 at a slower speed the flukes cut the water 

 laterally and obliquely downward. 



Less striking physiological phenomena 

 have been observed in the thermal adjust- 

 ments. Since the capacity of water for 

 conducting heat is 7.7 times as great as 

 that of air, whales would lose a vast 

 amount of body heat were it not for the 

 presence of a blanket-like heat-retaining 

 layer of fat over the whole body and the 

 absence of sweat or sudoriferous glands. 

 Whales in tropical waters need this 

 protection nearly as much as those in 

 temperate or cooler water, for the indi- 

 vidual body temperatures of whales are 

 higher than the water they frequent. 

 The body temperature of the Sei whale 

 (Balaenoptera borealis) is between 95 ° and 

 97°F., and that of the common harbor 

 porpoise (Phocaena phocoena) is 96°F. 



The hide of whales is endowed with 

 certain histological and structural features 

 that afford the maximum elasticity, and 

 conversely are capable of retarding increas- 

 ing compression on the thorax. The 

 fibrous blubber has tremendous strength 



and tenacity, for it will resist a strain of 

 several thousand pounds. Finbacks have 

 been known to drag a ship when the 

 prongs of the harpoon were merely 

 caught under the blubber on the back. 



Adjustments and modifications in the 

 structures that function in the process of 

 breathing were necessary to permit feeding 

 below the surface. Water would surely 

 get into the lungs during swimming with 

 a wide open mouth were it not for the 

 fact that a whale's narial passages do not 

 open into the throat as in land mammals. 

 A continuous tube between the narial 

 passages and the trachea or windpipe is 

 formed by an elongation of the arytenoid 

 cartilages and the epiglottis, which fits 

 into the soft palate. Other anatomical 

 and physiological adjustments have 

 come about to permit sustained submerg- 

 ence. Whales can remain submerged for 

 varying lengths of time, as a rule from 

 7 to 15 minutes, but in case of necessity 

 for 2. hours (Lillie, 191 5). Prolonged 

 submergence requires an adequate supply 

 of oxygenated blood, but it is also true 

 that the compression of the gases in the 

 lungs would raise the partial pressure of 

 the oxygen in the alveoli so that prac- 

 tically all of it could be consumed. Some 

 provision has also been made for the 

 absorption of the accumulated carbon 

 dioxide. 



The closing apparatus of the nose is 

 equally interesting, for closure is accom- 

 plished in an entirely different manner in 

 the two groups of living whales. The 

 toothed whales have a single external 

 nostril, while the whalebone whales have 

 a double nostril. In the case of the 

 toothed whales the narial cavity is di- 

 vided into a series of pockets into which 

 the narial passages open, and between 

 these pockets are a series of plugs con- 

 trolled by muscles that apparently con- 

 tract when pressure is exerted on the 



