Herrick, Brain of Certain Reptiles. 85 



ing the median cortex cephalad of the callosum "cortex am- 

 monis. " This region the writer termed fronto-median lobe and 

 cannot see how it is possible to so modify homologies as to com- 

 pare it with the Ammonshorn. It seems clear that it is the 

 limbic region — the sensory cortex of the mesal hemisphere 

 wall. 



Again the "intra-ventricular lobe" of the present writer 

 is called septum pellucidum or "fornix ridge" of Edinger. To 

 this usage we can only say that, if the term septum pellucidum 

 is used in the restricted sense as employed in mammals, where 

 it is limited to that part of the intra- ventricular walls which co- 

 alesce, it does not exist in reptiles. If the usage is extended 

 to embrace the entire intra-ventricular wall, it includes too much 

 and is liable to combine cortex and basal regions in one unnat- 

 ural assemblage. We cannot assent to Edinger's employment 

 of the term Fornix Leiste for the ventral median wall cephalad 

 of the callosum. Its use, if restricted to that part containing 

 the fornix fibres, makes it sufficiently identical with the corpus 

 fornicis to deserve that term. 



For a discussion of the septum, see Mihalcovics, p. 122, 

 especially these words: "Durch die Verwachsung der Hemsi- 

 phareninnenwande entstand vor dem 3. ventrikel eine solide 

 Masse, die durchsichtige Scheidewand (septum pellucidum) des 

 Saugethiergehirn. " 



The real nature of the cortex is well illustrated by a com- 

 parison of the embryonic condition of higher vertebrates with 

 that of Amphibia and Chelonia. (As Meyer well observes, 

 there are many points of resemblance between the amphibian 

 and turtle brain.) 



A comparison of Figs. 2 and 3, Plate XIX of Vol. II of 

 this Journal will illustrate the early condition of the cortex in 

 the snake and dog. It will be seen that the cortex proper is 

 derived from wandering neuroblasts whose points of develop- 

 ment were at the ventricular surface. The extent to which the 

 free neurons separate from the less differentiated cells near the 

 ventricle varies with age and with the group, as well as with the 

 region of cortex. It would seem that the simplest form of pal- 



