460 CETACEA. 



Those that I examined microscopically led me to regard them as identical 

 with the vasculo-lymphatic pulmonary glands already referred to in detail in 

 Orcella. 



Minute structure of Lung Gland. — If fig. 4, PI. XXXVII, being a microscopic 

 section of one of these glands from the king of Platanista, be compared with 

 figs. 3 and 5 in the same plate, respectively the stomach and pulmonary glands of 

 Orcella, the identity of all three becomes manifest. In each there is a copious 

 blood supply, the walls of the larger vessels, specially noticeable in fig. 4, being 

 obliquely perforated with orifices for subsidiary capillary tubes. These ramify 

 everywhere amidst the gland tissue. The basis of this latter is a fine retiform 

 connective tissue, the minute fibrillse in the meshwork of which radiate from points 

 which, under a high power, appear to be nucleate corpuscular centres. In the 

 meshes of the trabeculse are masses of much larger cells, in aU resj)ects agreeiag 

 with lymph corpuscles (fig. 4, c). 



Lastly, there are irregularly shaped and differently sized spaces, which to all 

 intents have the nature of lymph sinuses. The gland tissue proper or pulp is very 

 unequally distributed, not only as respects quantity, near or further distant from the 

 larger blood canals, but inter se a thickened patch appears surrounded by a space, 

 this latter again joined by sparse retiform tissue being encompassed by a dense 

 area of large corpuscular gland tissue. The aggregation of gland substance then 

 is most vai'iable, as are the open spaces or sinuses. 



Heart. — When fully injected with plaster of Pai'is the heart of Flatcmista 

 (PI. XXIX, fig. 1) is a great broad relatively short organ. It then measures some 

 6"50 taches across from border to border at the base of the ventricles. The ventricles 

 themselves are no more than 4'50 inches in length, but from the apex of the heart to 

 the upper tip of the distended auricle is 6"50 inches. Roughly speaking, then, the 

 heart is as broad as it is long. The ventricular apex exhibits a tendency to cleavage, 

 or indistinctly shows a bifid extremity, the incision being very shallow, and the more 

 lengthened left ventricle tending to the appearance of a double ajjex. The cavities 

 and valves offer few points of interest. One which simulates a pathological character, 

 though I believe it to be in this case normal, is the nature of the chordae tendinese. 

 These generally have a peculiar knotted aspect due to the swellings of a number of 

 ring-hke cartilages, which produce an appearance that may be likened to the nodular 

 character of the underground stem of the bamboo. 



Arch of Aorta and great vessels. — Three distinct vessels spring from the 



transverse portion of the arch of the aorta, as in Man and many other mammals, 



namely, a right brachiocephalic, a left carotid, and a left subclavian ; and from the 

 descending thoracic aorta arises the left posterior thoracic artery, as is sometimes the 

 case in the porpoise.' The brachiocephalic artery is of considerable length and, 

 above 2 inches from its origin, it gives off a small twig to the thyroid gland. 

 A little in excess of this distance it divides into two large branches, the first the 

 right carotid which passes forwards, and the second the right subclavian passing out- 



' Turner : Journ. Anat. and Phys., vol. ii, 1868, p. 68. 



