PRINCIPAL PARTS OF THE AMPBIBIAN BRAIN. 403 



Nevertheless, the brain of Meaobranchus is well worthy of examination upon the fol- 

 lowing grounds; — 



(1) The slight differentiation of the regions is an interesting reminder of the presumed 

 condition of all brains at an early stage of development. 



(3) The size of the cavities and communications and the thinness of the parietes permit 

 the efEeots of inflation with air to be at once apparent. 



(3) The Ldbi olfactorii are disconnected, as in all Vertebrates excepting the Anura. 



(4) The aula is large and well defined. 



§ 1057. The method of viewing the general constitution of the brain which was sug- 

 gested by Wy man and is herein adopted may be called the comparative anatomy way. There 

 is another, the embryological way, which is theoretically more satisfactory and complete, 

 but practically not well adapted to beginners. It would be well, however, for the some- 

 what advanced student to obtain a collection of foetal pigs, kittens, etc., of different ages, 

 and carefully expose their brains so as to observe the gradual increase of the hemispheres 

 and cerebellum, the formation of the gyri and the progressive thickening of the walls in 

 the greater part of their extent. 



§ 1058. Partial Vocabulary. — The following List includes only 

 the names of the principal parts of the Amphibian brain. A more 

 complete macroscopic vocabulary of the organ will be given later in 

 this chapter. 



Names of the Principal Parts of the Amphibian Brain, with 

 their more Common Synonyms.— A^3lsL—Y BniriGlQ of the " unpaired 

 cerebral rudiment." Aulatela— Atrophied or membranous roof of 

 aula. Auliplexus— Plexus choroideus aulse. Cerebrum— Hemi- 

 sphserse, larger portion of prosencephalon. Cerebellum— Dorsal 

 portion of epencephalon. Chiasma— Commissura optica, chiasma 

 nervorum opticorum. Conarium— Corpus pineale, pineal gland, 

 epiphysis. Crus cerebri— Floor of mesoccelia. Diaccelia— Ventric- 

 ulus tertius. Diencephalon — Deutencephalon, thalamencephalon. 

 Diaplexus— Plexus choroideus ventriculi tertii. Diatela— Atro- 

 phied or membranous roof of third ventricle. Endyma— Ependy ma, 

 lining of the ccelise. Epicoelia— Ventriculus cerebelli, cephalic part 

 ofventriculusquartus. Epencephalon— Hind brain. HemisphaBra 

 — Hemicerebrum. Hypophysis— Corpus pituitarium. Lobusolfac- 

 torius— Lateral half of rhinencephalon. Mesencephalon— Lobi 

 optici and crura. MesocoBlia- Ventriculus loborum opticorum, 

 aquseductus Sylvii, iter a tertio ad ventriculum quartum. Meta- 

 coelia— Caudal portion of ventriculus quartus. Metatela— Atro- 

 phied or membranous roof of ventriculus quartus. Metencephalon 

 —Medulla. Myelon— Chorda spinalis. Opticus- Lobus opticus. 

 Pia—Pia mater. Porta— Foramen Monroi. Portiplexus— Plexus 

 choroideus foraminis Monroi. Postcommissura— Commissura pos- 

 terior. Prsecommissura- Commissura anterior. Proccelia— Yen- 



