470 AJ^TATOMICAZ, TECSNOLOGT. 



" After a prolonged examination of many preparations, I am unable to define accurately 

 the limits of the fornix proper and the lyra (ly.). A comparison of the accounts given in 

 standard works with the appearances presented by the limited materials at my disposal 

 leads me to doubt whether the relative extent of the two parts in the human brain is 

 well determined." 



The fasciola (fid.) is thick, and no part of it presents the denticulations from which 

 its more ventral portion, in man, is called "fascia dentata." The peculiar curve of the 

 hypocampa, medicornu and fasciola is well indicated by the fact that the F. hypocampas 

 (F. hmp.), which corresponds nearly with them, in direction, is visible in this preparation 

 only at its two ends, near the splenium {sp.), and near the tip of the LI. hypocampae (LI. 

 hmp.). Between the fimbria and the fasciola is a depressed line which may be called the 

 Fissura fimbriae (F. fmb.). 



§ 1173.' Fig. 15.— The dorsal aspect of the proccelia. Prom Prep. 465 ; x 1. 



The special object of this preparation is to show that, in the cat, no part of the thalamus 

 appears in the pruccelia. The cerebellum (c6Z.) is shown only in outline. 



Both hemispheres were sliced from the dorsum to the level of the intermediate part of 

 the callosum (cl.). This laid open both procoelise in some degree. The central part of 

 each proccelia is called cella media {eel. m.). The right medicornu was then opened to 

 the tip, which, however, cannot be seen from the dorsal side. 



The floor of the proccelia is seen to be formed by the striatum (s.), the fornix (/.) and 

 the hypocampa (hmp.). The proplexuses have been turned in opposite directions for the 

 sake of showing the absence of any interval between the fornix and hypocampa — or the 

 fimbria which forms the border of the latter — and the striatum, such as would permit the 

 appearance of the thalamus in the proccelia. See Fig. 131. 



§1174. Fig. 16. — The rhinoccelia and proccelia. From Prep's 435 and 493 ; x3. 



This figure shows the continuity of the proccelia witli the rhinocoslia and its communica- 

 tion through the porta with the avla and diaealia. See § 1151. 



The right half of the brain was transected through the caudal part of the medicommis- 

 sura (mcs.). A slice was then cut from the mesal aspect so as to include the genu. This 

 exposed the praecornu {pi'cu.) with the mesal aspect of the striatum (s.), the rhinoccelia 

 (rhe.), and the relative extent of the pes (ps), and the pero (po.) of the Lobus olfacto- 

 rius. A bristle was then passed through the porta from the praecornu into the aula («.). 

 Just ventrad of the bristle are the praecommissura [prcs.) and the terma (t.). The latter 

 is traced distinctly to the chiasma {ch.), so that the cephalic wall of the coelian cavity is 

 complete. The deeper shadow just dorsad of the chiasma indicates the position of the 

 Recessus opticus (R. op.). 



Just dorsad of the bristle, the crista (C'ra.f.) is seen divided upon the meson, and con- 

 tinuous with the Columna fornicis (Olm.f). The indentation between the crista and the 

 praecommissura corresponds with the Recessus aulse (iJ. a.). The triangular Area sep- 

 talis {Ar. spt.), between the fornix and the callosum, is the mesal surface of the right half 

 of the Septum lucidum {8pt. lu.) and is in contact %vith its platetrope in the undissected 

 brain. The thickness of the hemisepta in the cai renders the adjective lucidum wholly 

 inapplicable. 



g 1175. Fig. 17. — The mesal aspect of the right hemisphere, with the Lobus 

 olfactorius. From Prep's 396 and 401 ; x 1. 



The caudal divisions of a hemiencephalon were removed, and the thalamus carefully 

 excavated so as to leave undisturbed the fornix (/.) and the fimbria {fnib.). In this 

 respect, this figure may be compared with the left half of Fig. 14. 



