PRINCIPAL PARTS OF THE AMPHIBIAN BRAIN. 403 



Nevertheless, the brain of Menobranchus 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. 



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

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



(3) The Lobi 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 Wyinan 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. Aula Ventricle 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. Diacoelia Ventric- 

 ulus tertius. Diencephalon Deutencephalon, thalamencephalon. 

 Diaplexus Plexus choroideus ventriculi tertii. Diatela Atro- 

 phied or membranous roof of third ventricle. Endyma Ependyma, 

 lining of the coelise. Epicoelia Ventriculus cerebelli, cephalic part 

 of ventriculus quartus. Epencephalon Hind brain. Hemispheera 

 Hemicerebrum. Hypophysis Corpus pituitarium. Lobusolfac- 

 torius Lateral half of rhinencephalon. Mesencephalon Lobi 

 optici and crura. Mesoccelia Ventriculus loborum opticorum, 

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

 ccelia 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. Pra3commissura Commissura anterior. Proccelia Ven- 



