220 ANATOMY OF THE CEXTBAL XERVOUS SYSTEM. 



in man; on the other, because Guclden, with a masterly hand for experimentation, 

 was able to tlirow abundant light on this very region of the anatomy of the fornix 

 by experiments on animals. 



The fornix longus has been demonstrated in man only recently by KoUiker. 



In many of the smaller animals the fibers of the psalterium, the decussations in 

 it, the decussation of the fornices longi, and the crura fornicis at their turning-point 

 into the depths of the central gray matter, together form a single thick mass, which 

 has been designated as the corpus forn'tcia. 



The olfactory lobe and the hippocampal lobe possess, in addition to 

 those mentioned, a number of tracts that are fitted to connect them with 

 one another or with other regions. Thns there runs dorsally on each side 

 of the median line of the corpus callosimi along its entire length a delicate 

 bundle of large fibers, the stria longitudinalis medialis, which, arising in the 

 dorsal regions of the hippocampal cortex, curves down anteriorly over the 

 corpus callosum and radiates into the septitm pellucidum. Then it is linown 

 that a long bundle, the cingulum, running in the gyrus fornicatus sends 

 tracts into the olfactory cortex, as well as into the other parts of the mar- 

 ginal gyrus. 



All these tracts belong to the cortical centers of the olfactory apparatus. 

 There are, however, connections between the olfactory apparatus and the 

 interbrain which must be very important, because they are well developed 

 in all animals, even in those without a cerebral cortex, and are everywhere 

 demonstrable. In order to understand them, we must return again to the 

 medulla of the lobus olfactorius. It is known that this arises, for the most 

 part, from the bulbus. Posteriorly it continues directly into the medulla 

 of the olfactory field. We have already become acquainted with one con- 

 necting tract of this "deep olfactory medulla": the olfactory bundle to the 

 cornu Ainnionis. 



The olfactory medulla possesses at least two other connections. One 

 of these tracts, consisting essentially of fine fibers, runs backward and can 

 be followed as far as into the region of the corpus mamillare. In its course it 

 must pass through the most ventral regions of the corpus striatum; but it 

 receives no fibers from this — as has been supposed. 



Certain of these fibers proceed still farther posteriorly, as far as into the region 

 of the ganglion interpeduneulare; perhaps into the fillet also. 



A second tract, originating essentially from the lateral parts of the 

 medulla of the olfactory area and passing through the forepart of the thala- 

 mus, rises to the inner surface of the ventricle, and passes along this, back- 

 ward to the ganglion habenula\ It is the tcBivia thalami. 



In a dog's brain, in which the entire cerebral cortex had been removed eighteen 

 months before death and the entire radiation from the mantle was wanting as a 



