3o6 WHALES 



of the body weight, those of some dolphins o-oi to 0-04 per cent and 

 those of Rorquals o-ooi to 0-003 P^^' cent. In other mammals, too, 

 the adrenals decrease in relative weight with increase of body weight. 

 This happens because they are intimately related to the functions of the 

 body surface. In the case of the Beluga and the race-horse mentioned 

 earlier, the adrenal glands weighed 1 1 ozs. and 1 1 ozs. respectively, the 

 race-horse having a bigger gland, no doubt because it is capable of sudden 

 spurts of energy. Similarly, such Felidae as cats and tigers which lie in wait 

 for hours, suddenly to pounce upon their prey with all their might, also 

 have fairly large adrenal glands. Such animals may be called 'sprinters' 

 whereas those who have to develop a constant but moderate quantity of 

 energy during a comparatively long time and those who live in a cold 

 climate may be called 'stayers'. Cetaceans in general may therefore be 

 regarded as stayers, and so it is not surprising at all that, compared with 

 most terrestrial animals, they have relatively large thyroids and com- 

 paratively small adrenals. 



On the floor of the brain, all vertebrates have a small gland - the 

 pituitary. It may be likened to a glandular switchboard since some of its 

 hormones control the function of the other endocrine glands, while others 

 have a direct effect on growth, lactation, sexuality, and other important 

 functions of the body. Some pituitary extracts play an important part in 

 medical therapy, and since the pituitary of cattle weighs no more than 

 0-07 ozs. (2 gm.), it is not surprising that repeated attempts have been 

 made to exploit the pituitary of Blue Whales (i| oz.) and of Fin Whales 

 (just under i oz.). True, this small organ lodged in a cavity, the sella 

 turcica, in the sphenoid bone at the base of the skull, is very hard to find, 

 but a recent method of cranial dissection has enabled biologists to obtain 

 the pituitary of every captured whale. 



In all mammals, the pituitary gland consists of an anterior and a 

 posterior lobe. Fig. 174 shows that the pale yellow stalk by which the 

 organ is suspended from the brain continues as the posterior lobe, the 

 anterior lobe being suspended from a stalk of its own, the so-called pars 

 tuberalis, which forms a ring round the posterior stalk and then runs on 

 into the tissue of the anterior lobe. It is dark brown in colour and consists 

 mainly of blood vessels supplying the anterior lobe, which is not as dark 

 as the pars tuberalis itself The anterior lobe accounts for much the largest 

 proportion of the mass of the pituitary, the ratio of anterior lobe, posterior 

 lobe and pars tuberalis being 16 : i : o-8. 



The fine structure of, and the circulation in, the Cetacean pituitary are 

 similar to those in other mammals, except that the former is distinguished 

 by having a septum between the anterior and posterior lobes. This septum 

 is made up of a fold of tough connective tissue thrown up from the dura 



