PANCREAS. 



99 



it is irregular. In the Carnivora it is always 

 large in proportion to the size of the animal*, 

 both the duodenal and gastro-splenic portions 

 being highly developed. In the ox, from the 

 distinctness of the two portions, the organ has 

 a bilobed appearance. In the horse, from the 

 gastro-splenic portion being double, it has a 

 trilobed form. But the most remarkable pan- 

 creas is that of the Rodents; it is spread out in 

 an arborescent manner, in an extensive mesen- 

 tery that imparts free movement to the long 

 duodenum, and extends towards the left in a 

 sort of omentum, which underlays the stomach. 

 (Fig. 74.) Confined thus between the two 

 layers of a mesentery, the ramified lobes of the 

 pancreas lie all in one plane. Although their 

 distribution is somewhat irregular, they more 

 or less radiate in their general direction from 

 the point at which the duct enters the intestine, 

 which in the rabbit is nine inches or a foot 

 from the pylorus. That part of it which occu- 

 pies the duodenal mesentery must be consi- 

 dered the representative of the duodenal por- 

 tion, and that spread out in the omentum 

 underlaying and attached to the stomach, as 

 the gastro-splenic. Altogether, this arbores- 

 cent pancreas of the Rodents is very volumi- 

 nous, particularly in the rat, from which the 

 drawing was taken. 



The pancreatic duct has in Mammalia gene- 

 rally the same branched character as in man, 

 the greater and lesser branches corresponding 

 to the lobes and lobules ; usually there is but 

 one orifice, rarely more, and most commonly 

 it enters the intestine near the pylorus, although 

 sometimes a great way removed from it. In 

 most of the Carnivora it is, as a rule, united 

 with the choledoc duct : in some cases it pre- 

 sents at the point of its immergence into the 

 intestinal canal a sort of ampulla, in which the 

 secretions probably mingle before their entry 

 into the intestine. There are, however, con- 

 siderable varieties of insertion in the lion 

 two pancreatic ducts join the choledoc sepa- 

 rately, one near the other. But whether 

 the ducts enter bv a common orifice, or by 

 two neighbouring ones, or whether there are 

 one or two pancreatic ducts, has, probably, no 

 physiological import whatever, as it cannot 

 make any difference whether the secretions 

 are brought into contact just before or just 

 after entering the bowel ; and this belief of 

 the non-essential character of these varieties 

 is strengthened, or rather proved, by their oc- 

 currence in closely allied species of the same 

 genus, and even in different individuals of the 

 same species. Cuvier says that he has ob- 

 served, although very rarely, in the domestic 

 cat, a lateral reservoir for the pancreatic secre- 

 tion, analogous to the gall bladder. Its duct, 

 about the size of the cystic, was an inch and a 

 half long before it united with a trunk formed 

 by the union of two pancreatic ducts, a prin- 

 cipal and an accessory, and, together with this, 

 formed a common duct analogous to the ductus 

 communis choledochus. Tiedemann has de- 

 tected a similar pancreatic reservoir in the 



* See the physiological portion of this article, 

 page li' l. 



common seal. The greatest distance from the 

 pylorus at which the pancreatic duct enters 

 the intestine occurs, I believe, in the Rodents. 

 In the rabbit this distance amounts to a foot 

 or upwards; and this arrangement, by giving a 

 considerable length of small intestine whose 

 contents are not acted on by the pancreatic 

 secretion, has afforded special facilities for ex- 

 periment. 



III. PHYSIOLOGY. 



Anatomy always implies physiology, 

 structure, function ; and the mind passes from 

 the one to the other by a ready and almost 

 irresistible transit. In fact, organisation is 

 but the accumulation, in certain parts, of 

 certain material agents, the sum of whose 

 common action gives as its result the func- 

 tion of the organ, and both the nature of 

 the elements so accumulated, and the method 

 in which they are built up, are determined 

 by, and have sole reference to, the work 

 to be done. Physiology invariably stands to 

 anatomy, even in its ultimate and minutest 

 details, in the relation of final cause. Now, 

 there are certain anatomical conditions that 

 always indicate physiological importance ; 

 among these are volume and constancy, 

 constancy in existence, and constancy in 

 structure. In all these respects we should 

 be led to infer from the consideration of the 

 anatomy of the pancreas that it possesses 

 essential functions ; for it is always of con- 

 siderable size, has a very wide range of exist- 

 ence, throughout the whole of Vertebrata, 

 from the lowest fish to the highest mammal, 

 and is analogically represented in many In- 

 vertebrata ; and, lastly, in structure it exhibits 

 with very few exceptions, throughout this 

 wide range, a remarkable sameness. 



The opinions entertained by the old ana- 

 tomists with regard to the office of the pan- 

 creas were many and various. The earliest 

 anatomical writers do not seem to have been 

 aware of its existence*; some thought that 

 its object was to underlay the stomach as a 

 cushion or pillow, and to serve for the dis- 

 tribution of vessels ; others, that it admitted 

 the chyle from the intestines ; others, that 

 it purified the dregs of the chyle ; others, 

 that it served for the spleen a purpose ana- 

 logous to that of the gall bladder for the liver ; 

 others, that by it were thrown off the gross 

 and used-up dregs of the blood ; others, that 

 the organ was formed for the reception of 

 the excretion of the nerves ; others, finally, 

 taught that the pancreatic secretion was not 

 only useful, but played a vital and essential 

 part in the organism. The first opinion, 

 which was of very ancient date, was held by 

 Vesaliusf ; but it is at once refuted by a 

 reference to those animals, birds and fish, for 

 example, in which the pancreas is frequently 

 remote from the stomach. The second view, 

 that the pancreatic duct admitted the chyle 

 from the intestines, is assigned to Baccius 

 and Folius, who both maintained that it 



* Hippocrates nowhere mentions it. 

 f De Humani Corporis Fabrica, i. 5. cap. 4. De 

 Omento. 



H 2 



