423 



ANATOMY OF VERTEBRATES. 



285 



before it enters the commencement of the wide intestine, near the 

 beginning of the spiral valve. The gall-duct in the Sturgeon and 

 Planirostra terminates at a greater distance above the valvular 

 intestine. The ordinary position of the entry of the bile into the 

 alimentary canal in Osseous Fishes is at the commencement of the 

 small intestine near the pylorus. The terminal part of the gall- 

 duct is usually slightly expanded, fig. 291, e, and its orifice is often 

 supported on a papilla, as in the Sturgeon, the Skate, and the 

 Labrax lupus. 



74. Pyloric Appendages and Pancreas of Fishes. - - In most 



Osseous Fishes the intestine 

 buds out at its commencement 

 into long and slender pouches, 

 or ca3ca, fig. 281, d, into which 

 it appears that the food does 

 not enter, and which, there- 

 fore, increase the direct secre- 

 ting surface of the alimentary 

 tract, over and above the ex- 

 tent of the mechanism for 

 pounding and propelling the 

 chyme, or of the vascular sur- 

 face which selects and absorbs 

 the chyle. By a very gradual 

 series of changes of these caecal 

 processes, within the limits of 

 the class of Fishes, they be- 

 come massed into a body, fig. 

 282, d, like the conglomerate 

 gland, called ' pancreas' in Man. 

 The secretion of the rudimen- 

 tal representatives of this gland 

 is so like the fluid which the 

 ordinary mucous surface of the 

 intestine eliminates and sets 

 free from its capillary system, 

 that conditions of the ordinary 

 alimentary tract exist in some 

 Fishes which render needless 



Alimentary canal of the Whiting (Merlanrjusvulgaris), {he deVelopemCnt of tll6 Sp6- 

 showiug the pile of casca around the pylorus, ccxxxi. . , 



cial accessory surfaces. JLne 



Dermopteri show no trace of pancreas ; their whole digestive 

 canal is simple : the organisation for which that canal is the 



