MILLER — CONTRIBUTIONS FROM ANATOMICAL LABORATORY. 227 



THE BRAIN OF Necturus ma.cula.tus. 



The brain of Necturus is long in proportion to its width and 

 depth. Its greatest length, measuring from the superficial ori- 

 gin of the olfactory nerves to the beginning of the spinal cord 

 is about 230 mm; its greatest breadth, measuring across the 

 caudal part of the prosencephalon is about 50 mm; its greatest 

 depth taken through the thalamencephalon at the origin of the 

 pituitary body is about 22 mm. 



Viewed from the dorsal side, PI. 12, and enumerating from 

 anterior to posterior we see that the brain is composed of the 

 olfactory lobes which pass without any sharp line of demarca- 

 tion into the hemispheres of the prosencephalon; back of the 

 prosencephalon, as an undivided body, lie the thalamencephalon 

 and mesencephalon and pineal gland ; then, as a caudal contin- 

 uation of the mesencephalon, we see the epencephalon which 

 forms a rudimentary roof of the fourth ventricle; and finally 

 sharply separated from the mesencephalon we can see the nieten- 

 cephalon or medulla oblongata. 



In a ventral view, PI. 13, we see the following parts : Lying 

 farthest anteriorly are the olfactory lobes and cerebral hemi- 

 spheres, then the thalamencephalon with its broad pituitary body 

 which covers the mesencephalon except on the lateral sides, and 

 finally we have the metencephalon. 



In a lateral view we notice that the brain vesicles lie in front 

 of one another and that there is but an insignificant departure 

 from the straight and unflexed condition of the embryonic 

 brain. This is true of most of the aquatic Urodeles as Fish 

 has noted. 



