1881.] ^^* [Wilder. 



The especial obj ect of this preparation is to show that, iu tlie cat, no part 

 of the thalamus appears in the procmlia. The cerebellum (cbl. ) is shown 

 only in outline. 



Both hemispheres were sliced from the dorsum to the level of the inter- 

 mediate part of the callosum {cl. ) . This laid open both proccelise in some 

 degree. The central part of each procoelia is sometimes called cella media 

 (eel. m.). The right medicornu was then opened to the tip which, how- 

 ever, cannot be seen from the dorsal side. 



The floor of the procoelia is seen to be formed by the striatum (s.), the 

 fornix (f. ), and the hypocampa (hmp.). The proplexus 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 procoelia. Whatever may be the case in man, neither in 

 the cat nor in any other mammal examined by me, is there any separation 

 of the borders of the rima more than will permit the intrusion of the border 

 of the velum to form the proplexus. 



It is commonly stated in works upon human anatomy that the thalamus 

 appears in the "lateral ventricle," forming part of its floor. It is possible 

 tliat the narrowness of the human fornix may permit this to occur ; but 

 the part of the thalamus so appearing must be covered by endyma, and 

 should be so described in contradistinction to the larger portion of its 

 dorsal aspect, which is certainly ectocoelian . However this may be in man, 

 it is not the case in any other mammal examined by me, and the explicit 

 statement in both the French and the English editions of Chauveau's 

 "Anatomy of domesticated animals," that the thalami appear in the 

 lateral ventricles in the horse, ox, pig and dog, and, by implication, all 

 other members of their, several groups, should not be accepted without 

 definite descriptions and figures. 



Fig. 16. — From preps. 425 and 493. Enlarged two diameters. 



This figure shows the continuity of the proecelia with the rhinocalia, and 

 its communication through the porta with the aula and diacoelia. 



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

 medicommissura {mcs.). A slice was then cut from the mesal aspect so as 

 to include the genu. This exposed the pracornu {prcu.) with the mesal 

 aspect of the striatum (s.), the rhinocoelia (rhc), and the relative extent of 

 the pes (ps.), and the pero (po.) of the Lobus olfactorius. A &r^«<^6 was 

 then passed through the porta from the prsecornu into the aula {a. ) . Just 

 ventrad of the bristle are the prcecommissura (prcs.), and the ferma (t). 

 The latter is traced distinctly to the chiasma {cli.), 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 (Crs.f.) is seen divided upon the 

 meson, and continuous with the Golumna fornicis (Clm.f). The indenta- 

 tion between the crista and the prtecommissura corresponds with the Re- 

 cessus aulce (R. a.). The triangular xl^'ea septalis {Ar. spt.) between the 



