376 CETACEA. 



membrane is not very tliick. The tliird stomacli is slmt off from the duodenum by 

 a broad flattened portion of the wall constituting a septum, in the centre of which 

 is the pyloric opening, about 0-12 of an inch in diameter. 



The duodenal sac' (fig. 5, iv.) is a capacious cavity which is rapidly contracted 

 into a very narrow tube one inch before the opening of the common bile duct. The 

 mucous membrane is smooth, but around the pyloric area, especially on the anterior 

 wall of the sac, there are rough areas of the same character as those of the third 

 stomach. A few pillar-like folds radiate from the pyloric septum which has a much 

 greater expansion on this than on its other side, and a few deep funnel-shaped pits 

 occm- between the folds. A few solitary glands are scattered here and there, but 

 there are no Peyer's patches. The gut-like portion of the duodenum (fig 5, d.) 

 available for observation, extends only to three inches. It is thrown into numerous 

 longitudinal and transverse convoluted folds, approaching in character to valvulse 

 conniventes, and at its commencement it is covered by numerous deep pits. 



Ilinute structure of the walls of the stomach. — As has been above stated, the 

 superficial aspect of the mucous membrane of the gastric ca^vities differs even to the 

 naked eye, so likewise when examined microscopically there are certain differences. 

 It may be as well, however, before mentioning these, to state that both in the case 

 of Orcella and of Platanista, a large series of microscopical preparations were made 

 by myself and partly by Mr. A. Stirling of the University Anatomical Museum, 

 Edinburgh, whose skill in microscopy and accuracy in manipulation are well known. 

 The specimens were prepared from materials which had been preserved in alcohol ; 

 staining by re-agents in some cases being adopted where clear definition of 

 textural character was desirable. Various preservative media were used, but most 

 of the specimens were of sufficient consistence to be mounted in Canada balsam. 

 Erom their oily nature Cetacean tissues are well known to anatomists to retain their 

 original characteristics intact and uninjured for a long period, and to be Httle 

 affected or altered by their alcoholic preservation. Hence those sketches delineated 

 in Plates XXXVI, XXXVII, and XXXVIII of dermal, visceral, placental, and other 

 parts of the round-headed and Gangetic Dolphins [Orcella and Tlatanista), and 

 most carefully drawn from the objects themselves vmder different microscopic powers 

 will be found to convey clear impressions of their minute structural peculiarities. 

 These will be described in detail, and will be considered, I trust, to have contributed 

 somewhat towards the elucidation of the minute anatomy, physiology, and organic 

 economy of at least two highly interesting genera of Cetacea. Those especially 

 which relate to certain glandular structures or organs, and to placentation are, I 

 conceive, highly important, in some cases corroborating and in others offering points 

 of divergence from facts and opinions expressed by such authorities as Eschricht, 

 Stannius, Ercolani, Elow^er, Turner, Alf. M.-Edwards, Murie, &c. 



To return to the stomach of Orcella: when sections are made, for example that 

 shown in Plate XXXVI, fig. 14, viz., a vertical section of the wall of the first cavity, 

 it is seen that this chamber, structurally, is but a passive recipient in the digestive 



' Cuvier, le?ons d'Anat. Comp. I™ Edit. t. v. p. 345, p\ xxxviii, fig. 2 ; Flowers' Lectures, I. c, p. 427. 



