380 THE ANATOMY OF VERTEBRATED ANIMALS. 



of the corpus callosum. The latter is remarkably short, and 

 directed obliquely backward and upward. It has no genu, and 

 the pre-commissural fibres of the ventricular wall spread out, 

 beneath its anterior end, upon the face of the hemisphere. 

 The part of the corpus callosum which answers to the lyra is 

 very thick in proportion, and is inclined at an acute angle to 

 the rest. 



In a transverse section, the corpus callosum is seen to be 

 very thin, and to curve upward and outward into the roof of 

 the ventricular cavity. The inner walls of the lateral ven- 

 tricles, which answer to the septum lucidum, are thick, while 

 tlie fornix is comparatively thin and slender. The anterior com- 

 missure is very stout. In this circumstance, as in the small 

 corpus callosum, the brain of the Hedgehog closely approaches 

 that of the Didelphia and Ornithodelphia. There is no trace 

 of a posterior cornu, or calcarine fissure, and the lateral ven- 

 tricle extends forward into the olfactory lobe. The optic nerves 

 are very slender ; the corpora geniculata externa are large and 

 prominent ; the nates are smaller than the testes, and trans- 

 versely elongated. The cerebellum has a large vermis and 

 small lateral lobes ; the floccuU are prominent and are lodged 

 in fossae of the periotic bones. The 2^072S Vay^olii is very 

 small ; the corpora trapezoidea proportionally large. 



The spinal cord is remarkable for its thickness, and, at the 

 same time, for its brevity, as it ends in the middle of the dorsal 

 region. As a consequence of this arrangement, the caiida 

 equina is particularly large and long. 



The stomach is simple, but the mucous membrane of the 

 considerable cardiac dilatation is thrown into numerous, and 

 very strong, longitudinal rugos. The intestine is about six 

 times as long as the body, and presents no distinction into 

 small and large ; nor is there any cascum. The liver is 

 divided by deep fissures into six lobes ; a central one which 

 bears the gall-bladder, a bifid spigelian lobe, and, on each side 

 of these, two other lobes. The pancreas is a large and 

 irregularly-ramified gland ; and the spleen is elongated and 

 trihedral. 



The pericardium is extremely thhi. The arteries arise 

 from the arch of the aorta, as in Man, by an anonyma, a left 

 carotid and left subclavian. The course of the internal 

 carotid is remarkable. When it reaches the base of the skull 

 it enters the tympanum and there divides into two branches, 

 of which one traverses the stapes, and, passing forward in a 

 groove of the roof of the tympanum, enters the skull and gives 



