96 



PANCREAS. 



white opacity, their fulness, that is, of a 

 densely opaque granular material prevents 

 their being seen to advantage as transparent 

 objects, or with a high power ; they are so 

 opaque that nothing of their structure can be 

 distinguished. When ruptured by pressure, 

 their contents escape, and are seen to consist 

 of two very distinct materials ; one, the afore- 

 said fine granular matter ; the other of clear, 

 spherical, uninuclear cells of about ^JQ of an 

 inch diameter. One would imagine ante- 

 cedently that these would hold the relation 

 to each other of secreting epithelium and 

 elaborated secretion ; but the cells are so clear, 

 so free from granular contents, and there is 

 such a complete absence of any intermediate 

 appearance, that I am at a loss in what way 

 to interpret them.* The duct opens by a single 

 orifice, and in a way admirably adapted for 

 preventing the regress of the secretion, or the 

 entry of the contents of the alimentary canal 

 into it. If the aperture in the centre of the 

 papilla by which the bile duct terminates is 

 opened up, it is found to lead into a lacuna, 

 or cul-de-sac, of about half an inch in length, 

 embedded obliquely in the walls of the in- 

 testine. At the bottom of this lacuna is a 

 second papilla, the real termination of the 

 pancreatic duct. Now, if the movableness of 

 the external papilla and the smallness of its 

 aperture were not sufficient to prevent the 

 ingress of the contents of the alimentary canal, 

 yet the very force that might drive in some 

 of these contents through the outer papilla, 

 would press the walls of the lacuna firmly 

 against the orifice of the internal one, and so 

 effectually close it ; nothing could be more 

 efficient than this form of double orifice. 



The duct in all reptilia always enters the 

 duodenum, generally separate, sometimes in 

 conjunction with the choledoch, and is almost 

 always simple. 



Aves. The pancreas of birds is propor- 

 tionally larger than in any other animals ; 

 and when we remember their deficiency in 

 salivary apparatus, its great development would 

 at once suggest a function, in some degree, at 

 least, supplementary to those organs. An- 

 other circumstance peculiar to birds and in- 

 dicative of the importance of the part that the 

 gland plays, is that the ducts are generally 

 many, two and three, and that they open by 

 separate orifices, and often at a considerable 

 distance from one another ; so that the secre- 

 tion may be poured forth on different and 

 widely separate portions of the alimentary con- 

 tents at one and the same time, a circum- 

 stance that must greatly increase and expedite 

 its action. 



Birds, we know, seize and swallow their 

 food generally without any mastication, and 

 therefore it is not until it gets to the gizzard 



* The follicles appear to contain only the granular 

 material, and in a minute duct I saw a number 

 of the nucleated cells. It is possible that they may 

 be a form of epithelium restricted to the terminal 

 ducts, by whose rupture and compression they 

 escaped, as the granular matter did from the fol- 

 licles. 



that it is subjected to any mechanical force 

 capable of breaking it up. This, therefore, 

 takes place immediately before entering the 

 duodenum, and this throws the function of 

 mastication close down to the pancreas, so 

 that from its situation, as well as in other 

 respects, it should have an insalivating function. 

 It is always enclosed between the two arms 

 of the duodenal flexure (Jig. 73.); the duo- 



Fig. 73. 



Pancreas of the common Goose (Anas anser), show- 

 ing its relation to the duodenum, its duplex form, 

 and its ducts. (Natural size.} 



denal portion of the gland being, so to speak' 

 alone developed. It is retained in this posi- 

 tion by the gastro-hepatic and gastro-colic 

 omenta, which sometimes simply attach it to 

 the border of the intestine, and sometimes 

 allow it to be free and floating. There is 

 considerable variety in its shape, but it is 

 always more or less elongated and slender : 

 sometimes it is undivided and single, in some 

 species deeply cleft, in others consisting of 

 two portions, or a double pancreas, quite dis- 

 tinct, each having its own duct ; sometimes 

 it is divided into three as in the pigeon. But 



