110 LABOKATORY OUTLINE OP NEUROLOGY 



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; Gray ('18), Figs. 732, 

 747, 748; Herrick ('18), Chap. XV; Morris ('14), Fig. 690, p. 

 877, also pp. 864-873; Piersol ('16), Figs. 1018, 1019, pp. 1180, 

 1181, Figs. 998-1000, pp. 1158-1161, Fig. 1002, p. 1163, Figs. 

 1004-1006, pp. 1165-1167; Sobotta ('11), Figs. 634-641. 



Master now, by the aid of text-books and diagrams, the ol- 

 factory system and its connections and relations as seen in the 

 sheep which is the same in plan as in the human brain. Re- 

 view the entire dissection, tracing the course of olfactory im- 

 pulses through the reflex pathways and centers of the basal 

 regions from the nose to the epithalamus and hypothalamus 

 and through the cortical pathways to the hippocampus and 

 thence again to the epithalamus and hypothalamus. This 

 gives a schematic picture of the workings of the entire rhinen- 

 cephalon. This should be done before further work is under- 

 taken and an analysis of these pathways fully written up. 



131. Now cut through the genu of the corpus callosum for- 

 ward and downward toward the olfactory bulb, thus opening 

 up the anterior horn of the lateral ventricle, which in the sheep 

 is directly continuous with the ventricle of the olfactory bulb. 

 (In the human brain the ventricle of the olfactory bulb is 

 obliterated in the adult.) 



132. Beginning now in the gyrus hippocampi at the most 



