METABOLISM 3O5 



is accordingly high. Human beings, too, have large thyroids, but for quite 

 different reasons which need not concern us here. 



Microscopic examinations of Cetacean thyroid glands have shown that 

 the organs may vary in output. This variation may, however, only reflect 

 the intensity of the hunt before the animals were killed. Thyroid extract, 

 which is used extensively for therapeutic purposes, can conveniently 

 be prepared from Cetacean glands. In 1941 Jacobsen established that 

 the effect of the hormone extracted from a given weight of glands was 

 about 67 per cent of the effect of the hormone extracted from the same 

 Aveight of sheep glands. However, all our existing plant is designed for 

 producing sheep's thyroid extract, and in Western Europe, at least, the 

 switch-over would be too costly to warrant new methods of extraction. 



The parathyroid gland, which measures only about 2 f inches x i^ 

 inches in large Rorquals, might be overlooked in animals some eighty feet 

 long, were it not for the fact that its grey or pinkish colour sets it off against 

 the dark red of the thyroid. It is found laterally behind either side of the 

 thyroid, and its weight varies from specimen to specimen (from ^ oz. to 

 4^ ozs. in Fin Whales). Undoubtedly this small gland has the same 

 function in Cetaceans as it has in all mammals, viz. control of the calcivmi 

 metabolism. 



Still more difficult to find are the adrenal (or suprarenal) glands, not 

 because they are particularly small (in large Rorquals each gland measures 

 8-12 inches x 6-8 inches x 2-4 inches, while both glands together weigh 

 from 28 ozs. to 88 ozs.) but because they are so tucked away between the 

 diaphragm and the front of the kidneys that they are extremely inacces- 

 sible. Generally, the adrenals are completely hidden by the stomach or the 

 diaphragm, organs which, in such enormous animals, cannot be easily 

 pulled aside. 



Bartholinus was the first to describe the adrenals of a porpoise as early 

 as 1654, but it was not until 1787 that Hunter described them in whales, 

 where they are flattish, oval organs, perceptibly lobular on the outside 

 (just like the thyroids) - a clear indication that the lobulation is connected 

 with the absolute size of the organs. (There are no lobes in porpoises and 

 dolphins.) On dissection, the adrenals, like those of all other mammals, 

 prove to consist of a yellowish cortex and a central brownish medulla, 

 from which biologists have managed to isolate cortine and adrenaline 

 respectively. However, the industrial processes involved have proved so 

 complicated and so beset with technical difficulties that there can be no 

 question of a serious exploitation of these Cetacean hormones at the 

 moment. Moreover, the adrenals are too poor in vitamin C (0-125 ozs. 

 per lb. of gland) to make their extraction an economic proposition. 



The porpoise's adrenal glands represent 0-04 to o -08 per cent 



u 



