BY G. ELLIOT SMITH. 657 



EXPLANATION OF FIGURES. 



Fig. 1. — Scheme of a sagittal section through the mesial wall of the cerebrum 

 of Perameles nanuta. The alveus fibres represented in a purely 

 diagrammatic manner. 



Fig, 2.— Ditto. Platypus. 



Fig. 3. — Ditto. Placental mammal. 



Fig. 4. — Scheme of the hippocampus as seen in ti'ansverse section through 

 the region of its commissures. The cells, axis-cylinders and 

 collaterals shown as they are stained by (iolgi's method. 



Fig. 5. — Mesial view of " hippocampal region" in pig (fcetal) to show the 

 S-shaped bend of the hippocampus; only the posterior part of 

 the corpus callosum represented. 



References to Jigtiref. 



ac, anterior commissure; a/., anterior pillar of fornix; alv., alveus; 

 c, "collateral" of an alveus fibre, ending in the stratum radiatum; cc, 

 corpus callosum; d., molecular layer of the fascia dentata; df., descending 

 alveus fibres (to form the anterior pillar of fornix and the precommissural 

 fibres); exf. off., external olfactory root; /., fibres of alveus, represented 

 schematically; FD., Fascia dentata; /r"., fimbria; g., pyramidal cells of the 

 hippocampus; h/., hippocampal fissure; hip., hippocampus; int. caps., 

 internal capsule lying in the corpus striatum; I., bundle of collaterals (so- 

 called superficial medullary lamina) derived from the pyramidal cells of the 

 hippocampus, also transverse sections of bundles of longitudinally running 

 fibi-es; M., foramen of Monro; ^9., Purkinje-like cell of tlie fascia dentata; 

 ps^., dorsal limb of the iiippocampal commissure; ps'^ ., ventral limb of the 

 hippocampal commissure (the psalterium of placental mammals); pyr., 

 pyramidal cell of the subiculum cornu Ammonis; rf., rhinal fissure; s., pre- 

 commissural fibres of the fornix-system; se^H., "septum pellueidum "; 

 s. hip., subiculum cornu Ammonis; spl., splenium corporis callosi; spl'^., 

 ^' splenium of the hippocampal commissure.''' 



