PARTS AND FEATURES 



about once per second, and yet he has seen one recover from 30 minutes 

 of complete submergence, while he had heard of one doing so after 

 45 minutes. Burrell (1927) found that the adult platypus can remain 

 under water for the duration of 5 to 10 minutes, while the new born 

 youlig can survive a submergence of three and a half hours. Parker 

 (1922) reported that a large manati at rest was in the habit of staying 

 down for a period varying from 7 minutes to 16 minutes and 20 seconds, 

 then arising to the surface for as much as three minutes and taking sev- 

 eral breaths. A younger animal arose oftener, and fishermen told him 

 that when these beasts are being hunted they may stay below for half 

 an hour. 



An experienced whaler whom I consider trustworthy has assured me 

 that when it "sounds" a humpback will ordinarily stay down from 

 8 to 12 minutes, with observed maximum of 23 minutes; finback, 8 to 

 12, with 28 as a maximum; bowhead, 12 to 15, with 30 minutes as a 

 maximum ; and cachalot from 30 to 60 minutes with an observed maxi- 

 mum of one hour and 45 minutes. Andrews (1916) has quoted an 

 instance where a blue whale sounded for 50 minutes, reappeared to 

 spout 20 times and then disappeared for another 40 minutes. Cer- 

 tainly there is abundant evidence that the cachalot can easily submerge 

 in excess of an hour, but records of over two hours should be viewed 

 with suspicion. Certain other of the larger Odontoceti (as Hyperoodon) 

 are notable for the speed with which they seek great depths when har- 

 pooned, and for the length of time that they can stay there. The 

 Mysticeti are evidently less gifted in this respect, and it is doubtful 

 whether this ability is as well developed in porpoises with littoral pre- 

 dilections. 



That lengthy submergence is not fatal to the sloth and young platy- 

 pus is doubtless chiefly attributable to their low rate of metabolism, and 

 armadillos and ant-eaters should be expected to exhibit the same accom- 

 plishment. This has also been advanced not infrequently as the pos- 

 sible explanation of why whales are also able to suspend breathing 

 for so long. There is no evidence to show that in any marine mammal 

 the rate of metabolism is low, and several particulars indicate that it 

 is high, among which are details of the lungs, blood and the tempera- 

 ture. In Tur stops the latter is about 36 degrees Centigrade. So in the 

 Cetacea I am inclined to believe for the present that what may be desig- 

 nated as the normal rate of metabolism is not low. But some fish are 

 known to be able to contrive, by some obscure means, to lower their 

 rate of metabolism very quickly when it is advantageous for them to 



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