20 MARINE AND AQUATIC TRESPASSERS. 



and so allowing them to roll harmlessly over his 

 head. 



It is therefore absolutely necessary that the whale 

 should be able to pass a considerable time beneath the 

 surface, and be for that time deprived of the power of 

 respiration. How can we reconcile these conflicting 

 necessities ? 



The first and most obvious suggestion is, that the 

 animal should be supplied with an internal apparatus, 

 by means of which it can take down with it a supply 

 of air that will suffice for respiration during the time 

 of submergence. But, considering that the ordinary 

 time during which the animal is under water is about 

 an hour, and that it must be capable of extending that 

 time if needful, it is evident that the air-vessel would 

 be so large that the whale would be absolutely incap- 

 able of sinking at all. 



This plan, therefore, is not feasible, and we must 

 look for one which will give a supply of arterialized 

 blood while the whale is under water. Suppose that, 

 instead of giving to the whale a supply of air which 

 will oxygenate the blood, it should have a reserved 

 supply of already oxygenated blood, which can be 

 passed into the system when required. 



In fact, suppose that the whale has the power of 

 acting, with regard to respiration, as the camel does 

 with drink, and is enabled in a few minutes to oxyge- 

 nate as much blood as will serve the purpose of life 

 for an hour or more. If this can be done, the problem 

 is at once solved, for the blood-reservoir will be very 

 small when compared with the air-reservoir, and, not 

 being lighter than the rest of the body, will not 



