THE ELASMOBRANCH FISHES 



137 



enters the duodenum in such a way as to form two miniature blind sacs (sc.^"^) . 

 In Laemargus rostratus (fig. 136b) the blind sac is divided so that the proxi- 

 mal part of the intestine appears as a bilobed structure. Into one of the lobes 

 the pylorus enters. 



The ducts from tlie liver (d.ch., fig. 137b) and pancreas (p.d.) enter this 

 middle or duodenal part of the intestine as in Heptanchus, and their entrance 



Fig. 136. The duodenum. A. Spinax niger. (From Eedeke.) 'B. Laemargus rostratus. (From 

 Helbing.) 



d.ch., bile duct ; p.v., pyloric valve ; py., pyloric stomach ; sc.^~-, first and second blind 

 sacs; spl., spleen. 



marks the region from which the liver and the pancreas arose in the embryo, 

 the length of the ducts in the adult showing how far the two organs have ])e- 

 come separated from their place of origin. 



LIVER 



The liver in the adult consists of a right and a left lobe, connected solidly an- 

 teriorly as in Heptanchus (see fig. 119) . From the posterior part of the union 

 of the two lobes a caudate lobe may arise. In this or in either of the other lobes 

 the gall bladder may be located. The main lobes of the liver are character- 

 istically large in the sharks and may extend the entire length of the coelom. 

 In some of the larger sharks (Cetorhinus) as much as five barrels of oil are 

 reported to have been obtained from the liver of a single specimen. In the 

 rays the lobes are less well developed, but here, too, they are often large. 



Bile secreted by the liver is collected by a series of tubules some of which 

 empty into the gall bladder. The gall bladder is drained by a duct w^hich, 

 joined with other ducts from the liver, is the ductus choledochus. This duct 

 in Squalus sucklii (d.ch., fig. 137b) reaches the intestine at its proximal part 



