106 LABORATORY OUTLINE OF NEUROLOGY 



tirely covered by the gyrus hippocampi with which its tissue is 

 confluent. On its ventral side is a subsidiary convolution, the 

 gyrus dentatus (fascia dentata), and it gives rise to a sheet of 

 fibers, the fimbria, which passes forward in the floor of the 

 lateral ventricle to enter the body of the fornix (corpus fornicis, 

 an unpaired mass of fibers under the splenium of the corpus 

 callosum). Here some of the fibers cross to the other side 

 forming the commissura hippocampi, the entire complex forming 

 the lyra. Others descend into the diencephalon as the columna 

 fornicis (Section 129). 



128. The hippocampus. — Make a cross-section through the 

 hippocampus and lobus hippocampi and draw the cross-section, 

 showing the relation of the fimbria, hippocampus, and gyrus 

 dentatus. Note that this section is not transverse to the whole 

 hemisphere in this region, but only to the hippocampal forma- 

 tion. 



129. Column of the fornix. — Now from the body of the fornix 

 follow the column of the fornix (columna fornicis), dissecting 

 it out as you go, forward to a position just above the anterior 

 commissure and then backward and ventrally to the mammil- 

 lary body (see Burkholder ('12), Plate XX). A small part may 

 be seen to turn back immediately behind the interventricular 

 foramen to enter the stria medullaris and so reach the habenula. 

 The column of the fornix consists mainly of fibers passing out 

 of the hippocampus by way of the fimbria into the olfactory 

 correlation centers of the hypothalamus and epithalamus. 



The column of the fornix is the efferent projection tract from 

 the olfactory cortical center (hippocampus) to the mammillary 

 body and habenula; that is, it carries motor impulses from the 

 olfactory cortex to the diencephalic olfactory centers. From 

 these latter centers these impulses are carried by the same 

 tracts as those from the subcortical reflex centers; see Section 

 125 (7) to (10). 



130. The following references to figures of the human brain 

 will aid in understanding the relations of the olfactory ap- 

 paratus of the sheep: Barker ('01), Chap. LII; Cunningham 

 ('15), pp. 623-628, also Fig. 566, p. 637; Herrick ('15), Chap. 

 XV; Morris ('14), Fig. 690, p. 877, also pp. 864-873; Piersol 

 ('13), Figs. 1018, 1019, pp. 1180, 1181, Figs. 998-1000, pp. 



