NAMES OF THE ENCEPHALIC CA VITIES. 407 



The Greeks designated eitlier a cardiac or an encephalic cavity by the name KoiXia, and 

 the senior author has proposed (.9, 125, J J, 540) to substitute it for ventrieulus, and to des- 

 ignate the several enceplialic cavities by terms formed by its combination with the charac- 

 teristic prefixes of the encephalic segments. Tliis gives us rhiiiocodia, procwUa, diaccdia. 

 mesocmlia, cpicalia and metaeislia. These terms are capable of inflection, and the longest 

 of them is no longer than the Latin ventriculus, which requires a prefix or qualifying 

 word. Finally, when the student has once learned the order and significance of the names 

 of the encephalic segments, lie has only to acquire a single term and apply thereto tlie cliar- 

 acteristic prefixes with which he is already familiar. 



§ 1065. Aula and Porta. — These names were proposed by the senior author (3, 9, H, 

 540) upon the following grounds :— 



(1) To substitute brief single words for the phrases; " ventriculus communis," " ven- 

 triculus lohi communis," cavity of the " cerebral rudiment," unpaired hemisphere vesicle 

 or "secondary forebrain," mesal part of the "common ventricular cavity," foramen 

 Monroi, etc. 



(3) Because the phrase most commonly employed, /oraswe/t Monroi, is used to designate 

 at least three different cavities or orifices : (A) The cavity by which either proccBlia com- 

 municates with the mesal series of coelise ; (B) the two lateral orifices together with the 

 intervening space ; (C) the mesal (cephalic) orifice of the diacoelia. We have been unable 

 to ascertain by whom the phrase was first employed, and the description by Monro sccun- 

 dus (A, 13-16), in whose honor it was applied, is somewhat vague (Wilder, 3). 



(3) In order to indicate our opinion of the desirability of recognizing the aula as mor- 

 phologically an important element of the cceliau series. 



§ 1066. TelcB and Plexuses. — The atrophied or membranous roofs of certain coelite are 

 called tela vasculosa or tela choroidea, superior, inferioi; etc., and the vascular plexuses 

 formed by them are designated as plexus choroideus ventricuU tertii, etc. If once the 

 general names for the encephalic segments and coeliae are adopted, we have only to employ 

 the characteristic prefixes and gain the single and definite names metatela, diatela, aula- 

 tela, metaplexus, diaplexus, auliplexus, portiplexus and proplcvus. 



§ 1037. Commissurm. — Of the bands of fibers, or aggregations of cells and fibers, by 

 which the parts of the brain — especially corresponding parts upon the two sides — are con- 

 nected, some are called commissures, while others have received special names. These 

 latter — eallosum, fornix, pons and chiasma — are retained, but the other three — as proposed 

 by the senior author (W, 136, 14, 538) — are here simplified by prefixing to the word com- 

 missura the syllables prw, post and mecli. 



% 1068. Tabular View of the Encephalic Segments and their parts in the Ampliibian 

 Brain. — The accompanying Table contains the names of the principal parts of the brains 

 of the frog and ilenobranchus arranged according to the segments which they constitute 

 (Fig. 110-113). Attention is called to the recurrence of the prefixes characterizing the seg- 

 ments in the names of tlie corresponding caiiiv, telm and plexuses (§ 1066). A somewhat 

 similar table is given by Mihalkovics (A, 48), including also the names of the parts of the 

 mammalian brain ; see also Quain (A, II, 755). 



The abbreviation an. indicates that the part is azygous or unpaired ; the rest are lateral 

 and paired. 



