3o6 



NERVOUS SYSTEM OF VERTEBRATES. 



folded into the ventricle to form the choroid plexus. The recessus 

 neuroporicus is recognizable in the frog a little above and in front 

 of the commissure as in Petromyzon. The caudal part of the 

 roof is produced dorsally into a more or less branched sac, the 

 paraphysis. The median ventricle is connected by wide foramina 

 of Monro with the lateral ventricles, which extend forward into 

 the olfactory bulbs and backward into the rounded posterior 



Nuc. habenulae 

 Tr. olf.-habenulari 



Tr. haben.-pedunc. 



ippocampus 



Tr. olf.-cortic 

 Bulbus olf. 



-A . 



Tr. olf. 

 Tr. olf.-hypothal. nied. / 



Upper commissure 

 Lower commissure 



Nuc. praeopticus 



Tr. strio-thalam. 

 Tr. lobo-epistriaticu 



Fig. 150. — A diagram of the fiber tracts in the forebrain of a tailed amphibian, 

 Necturus. The representation of the commissure is based wholly upon Weigert 

 sections of the brain of Necturus. In drawing the other tracts the descriptions of 

 P. Ramon, Van Gehuchten and Bochenek for other amphibia have been consulted. 

 The tractus olfacto-hypothalamicus lateralis is represented as joining the tractus 

 strio-thalamicus from above and going off from it to the inferior lobe. 



part of the lateral lobes. For the purpose of describing centers 

 and fiber tracts there may be distinguished in the lateral lobes a 

 base or ventral wall, a lateral wall, a rooj and a mesial wall. It 

 will be convenient to anticipate the results of the following dis- 

 cussion and divide the mesial wall into a portion in front of the 

 foramen of Monro called the septum (precommissural or parater- 



