221 



The large trilobed yellowish liver is attached by the 

 suspensory or falciform ligament to the front wall of the 

 abdominal cavity. Partly embedded in the liver, between 

 the right and median lobes, is the gall-bladder ; its cystic 

 duct and two hepatic ducts unite to form the common bile 

 duct, which opens into the intestine (duodenum) just be- 

 hind the pylorus on the convex side of the sharp bend. The 

 whitish bilobed pancreas is closely applied to the intestine ; 

 and from its small ventral lobe within the pyloric bend, 

 the pancreatic duct passes into the intestine almost opposite 

 where the bile-duct enters. A dark red organ in the loop 

 of the stomach is the spleen. 



The Dogfish has a bilobod liver, and the gall-bladder is 

 embedded in the upper part of the left lobe. The pan- 

 creatic duct enters the intestine, ventrally, about an inch 

 from the pylorus. 



Describe the Brain of Raia and of Scyllium. 



See page 201. In Raia and Scyllium the cerebral hemi- 

 spheres are not distinctly separated. The olfactory lobes 

 (strongly developed) are the expanded ends of two stout 

 stalk-like extensions of the cerebrum, and are closely 

 connected with the olfactory sacs. 



Write an Account of the Cranial Nerves, their Branches and 

 Distribution. 



The nerves marked * are sensory or afferent, i.e., receiving impres- 

 sions and transmitting these to the brain ; those marked f are 

 motor or efferent, i.e., transmitting impulses from brain to body. 



There are ten pairs of cranial nerves. (For origin, see 

 pages 201, 202) : 



I. The *olfactory nerves (so called) are the thick stalk- 

 like extensions from the cerebrum. The true olfactory 

 nerves are the small nerves between each olfactory lobe and 

 the folds of each nasal sac. 



II. The *optic nerves, arising from the optic thalami, 

 cross and interlace (optic chiasma) on the floor of the 

 thalamencephalon, and pass through the orbits into the 

 eyes (retina). See eye, page 203. 



III. The slender foculomotor arises from the ventral 

 surface of the mesencephalon, anteriorly. Entering the 

 orbit it there .gives off branches to four of the six muscles 

 of the eye, namely, the rectus internus, superior, and 

 inferior, and the obliquus inferior. 



