

FROM THE ANATOMY OF A PORPOISE. 59 



of their encapsulation in an external coat of fibro-cellular tissue, and 

 their want of such supporting elements within their parenchyma 1 . 



There can at all events be no doubt that they were developed 

 from the general formative mass of blastema, which surrounds the 

 aorta in the foetus, as described by Professor Goodsir 2 ; and that 

 therefore they were morphologically as well as physiologically to 

 be classed with the thymus 3 . This gland, as well as the thyroid, 

 was largely developed in this specimen, and the arrangement of the 

 two glands coincided very exactly with the description given of 

 them by my friend Mr. Turner 4 . 



The lymphatic glands generally throughout the body were 

 largely developed ; so largely, in fact, at either jaw angle, as to 

 simulate the appearance of a large submaxillary gland. The spleen 

 was, as has been so often described, curiously multifid. 



All of these ductless, all of these lymphatic glands were richly 

 supplied with blood vessels ; all, alike and jointly, laboured at the 

 elaboration of the constituent elements of the vast mass of this 

 cetacean's blood. They enabled it thus to support a high standard 

 of temperature in an excellent conducting medium, and they sup- 

 plied all the calls for rich and refined aliment which a brain equalling 

 in this case one-sixtieth of the weight of the entire body made upon 

 the nutritive fluids. They may be taken as illustrations of ' tauto- 

 geneous growths ' of the first of our two classes. 



Many of Mr. Paget' s instances of complemental nutrition Mr. 

 Darwin would explain as the results 5 of hereditary transmission, 

 with modification, and there can be little doubt that of the two 

 hypotheses the latter will to many minds seem to suit the better 

 with such instances as the four rudiments of nails on the fins 

 of the manatee, or the equally rudimentary teeth in the ruminant's 



1 Though my dissection enables me to confirm the views put forth by Mr. Turner, 

 it compels me to dissent from those anatomists who say there is nothing in the 

 Cetacean economy to represent either the Vena Azygos or the Cowper's Glands of 

 Human Anatomy. 



2 'Phil. Trans.' 1 846, p. 638. 



3 In the common shrew, however, two bodies are to be found, floating loosely in the 

 abdominal cavity, but anchored each by a process of mesentery which is attached just 

 where these bodies in the porpoise lie fixed ; and that they are connected with the 

 lymphatic, or rather with the lacteal system, an examination of a shrew, which has died 

 whilst digesting, will leave no doubt. 



4 ' Transact. Royal Soc. Edinburgh,' vol. xxii. part ii. 



5 'Origin of Species,' pp. 453-454, Ist e( *it. J PP- 486-487, 3rd edit. 



