652 'Journal of Comparative Meiirology and Psychology. 



part of the base of the claustrum, and very near the base of the 

 lenticular nucleus, as it passes over to the frontal lobe, I shall refer 

 to it in this paper as the fasciculus occipito-frontalis infenor, or 

 briefly as the fasciculus. 



The fasciculus occipito-frontalis inferior is a large associating 

 l>undle of fibers uniting, as its name indicates, the occipital with the 

 frontal lobe. It also contains fibers which join the frontal lobe with 

 the posterior part of the temporal and parietal lobes. While the 

 greatest number of its fibers proceed directly to the occipital lobe 

 and can be there recognized as a more or less distinct bundle, yet 

 before it has reached this lobe a number of its fibers have turned off 

 and terminated in the cortex of the posterior part of the temporal 

 lobe and also in a small portion of the posterior part of the parietal 

 lobe. From all parts of the frontal lobe the fibers of this fasciculus 

 can be traced converging to a single bundle which swings round the 

 lower external side of the nucleus lentiformis, at which place it 

 appears as a distinct bundle, the cross section of which has an area 

 of about one fourth inch or more. It proceeds for a short distance 

 as a distinct and almost round bundle, and again spreads out to a 

 fan shape as it approaches and enters the occipital lobe. Its lower 

 fibers sweep round so as to embrace the posterior horn of the lateral 

 ventricle, as shown in Plate II, Fig. 4, and more distinctly in Fig. 3 

 (F. 0. f. i.^). From the anterior extremity of the island of Reil to 

 the end of the posterior horn of the lateral ventricle the fasciculus 

 occipito-frontalis inferior has certain definite and well-marked rela- 

 tions with the surrounding structures which must be referred to in 

 order that we may understand its exact position. At the outset I 

 would emphasize the fact that as it swings to the lower external side 

 of the lenticular nucleus and the external capsule it stands out with 

 striking distinctness and is at once recognized as a separate bundle 

 isolated from the surrounding structures by the directness and com- 

 pactness of its fibers. I have stated in my description of the methods 

 employed in this work, the law that when fibers from a adjacent parts 

 are proceeding to distant adjacent parts, they tend to gather together 

 to form a bundle and thus proceed as far as possible before spreading 

 out to their point of distribution. At the place in question — ^low 



