156 WHALES 



The decrease of blood-flow to the muscles of aquatic mammals and the 

 consequent increase to the other organs would naturally lead to a great 

 distension of the blood vessels in the latter, and a contraction in the 

 former. That this is in fact the case was discovered by Irving and his 

 collaborators, who found that the blood pressure in the large arteries 

 supplying the muscles was increased, while it was greatly decreased in the 

 smaller arteries. Somewhere between the large and small arteries, a 

 contraction of the vessels must therefore take place. In fact, hardly any 

 blood can be drawn from the muscles or the intestines of a diving animal. 



The Norwegian physiologist P. F. Scholander, whose work we have 

 discussed in the last chapter, took an electrocardiogi^am of a porpoise 

 swimming at the surface, from which it appeared that the animal had a 

 pulse rate of about 130 beats per minute. These figures agree with the 

 available data on Bottlenose Dolphins and also with a nineteenth-century 

 count made by Eschricht (150 beats a minute). Accordingly, the Beluga 

 would have a pulse rate of about 30 at the surface, and the bigger whales a 

 correspondingly lower rate - which was calculated by Putter (1924) to 

 be no more than 5 beats a minute. On 5th December, 1959, a 45-foot 

 Fin Whale was stranded alive at Cape Cod. The animal lived for 24 hours 

 and during that time its electrocardiogram was taken by J. Kanwisher 

 (Woods Hole). It showed a heartbeat of 25 a minute. Because the 

 respiratory rate of the stranded animal was three times as fast as in a 

 normal swimming whale, we may assume that the pulse rate of a normal 

 Fin Whale is about 8, which agrees quite well with Putter's calculations. 



Although the available data are still far too few for a final conclusion 

 to be drawn, we may say provisionally that, judging by body weight, the 

 heartbeat of the smaller dolphins, at least, is abnormally accelerated at the 

 surface. We can therefore say that the pulse rate is normal in diving, and 

 increased in surfacing. This is not so peculiar when we consider that 

 Cetaceans are permanent aquatic animals which, after all, have to re- 

 plenish the oxygen in their blood very quickly during the short time they 

 are at the surface. Belugas, and perhaps the bigger whales also, would 

 then be the exceptions to the rule, for their pulse rate seems normal at the 

 surface, and abnormally low below. 



By and large, therefore, the pulse rate itself gives no indication that there 

 is anything special about the output of the Cetacean heart, particularly 

 since little is known about the blood pressure, for though Putter thought 

 it must be very low in big whales, his data require further confirmation. 

 Only one anatomical facet of the problem has been more fully investi- 

 gated, viz. the extension of the elastic part of the arterial system. 



From our pulse and from spurts of blood from a severed artery it is 

 clear that the blood in our arteries does not flow evenly, but intermittently. 



