272 On the Cingulum, fyc., of the Marmoset Monkey. [June 19, 



with the brain of man. Moreover, the slight amount of convolution 

 on its median surface is a very great advantage in tracing fibres ; 

 this is especially the case with the calloso-marginal sulcus, the 

 absence of which enables the fibres of the cingulum to be followed 

 in a way not obtainable in the brains of other apes and of man. 



The cingulum, or the fibres of the gyrus fornicatus, is described in 

 three parts : 



1. Horizontal, above the corpus callosum; 



2. Anterior, in front of this body ; 



3. Ppsterior, from behind the corpus callosum to the anterior end 



of the temporo-sphenoidal lobe. 



The horizontal part consists, not of fibres extending through its 

 whole length, but of internuncial fibres coursing between the gyrus 

 fornicatus and the centrum ovale ; the anterior part connects the 

 olfactory nerve with the frontal region ; the posterior part contains 

 internuncial fibres between the gyrus hippocampi and the inferior 

 surface of the temporo-sphenoidal lobe. 



The cingulum is not connected with the hippocampal lobule and 

 its contained nucleus amygdalae, as was considered by Broca. 



Reference is made to an operation in the monkey, performed for 

 the author by Professor Horsley, in which the cingulum was divided, 

 producing degeneration in it in a posterior direction. 



From the relation of the gyrus fornicatus to sensation found by 

 Professors Horsley and Schafer, it is suggested that the cingulum 

 joins this gyrus representing sensation with the part of the centrum 

 ovale connected with the so-called motor cortex. 



The calcarine fibres bounding the calcarine fissure are described as: 

 internuncial fibres analogous to the cingulum, and the superficial fibres 

 of the gyrus fornicatus are considered to be a separate tract and not 

 part of the cingulum. 



The posterior part of the corpus callosum is described in three 

 parts : 



1. The body, giving off the tapetum to supply the cortex bounding 



externally the posterior and descending cornua of the lateral 

 ventricle. , 



2. The splenium, ending in the forceps major, sending fibres to the 



inner part of the occipital lobe below the calcarine fissure. 



3. An intermediate part between the two former, forming with the 



tapetum the roof of the posterior cornu, and supplying the 

 cortex of the upper lip of the calcariue fissure. 



No connexion between these fibres and those of the internal capsule, 

 as described by Professor Hamilton, can be found. 



The fornix comprises the body and the posterior crura. The 

 body can be separated, while in the septum lucidum, into (1) a 



