COMMISSURAL FIBERS. 



235 



opposite temporal and occipital lobes together (pars occipito- 

 temporalis], the limbic lobes with the contra-lateral olfactory 

 tracts, and the olfactory tracts with each other (pars oljactoria). 

 It is supplementary to the corpus callosum and associates regions 

 not joined by the great commissure, especially the cortex of the 

 tentorial areas of the cerebral hemispheres. In size it varies 



Fig- 73- Transverse section of cerebrum, cutting corpus callosum, anterior 

 commissure and optic chiasma. Viewed from front. Commissural fibers. 

 (Morris's Anatomy after Toldt.) 



a. Caudate nucleus (head), b. Internal capsule (frontal portion). Lentiform nucleus: 

 c. Putamen, d Glpbus pallidus. e. Medullary lamina, f. External capsule, g. Claustrum. 

 h. Vena terminalis. i. Interventricular foramen (Monroi). j. Anterior perforated sub- 

 stance, k. Uncus. 1. Anterior commissure, m. Longitudinal fissure, n. Corpus callosum. 

 o. Anterior horn of lateral ventricle, p. Chorioid plexus of lateral ventricle, q. Septum 

 pellucidum. r. Columns of fornix. s. Lateral fissure (Sylvii). t. Gyri of insula. u. Optic 

 recess, v. Optic tract, w. Optic chiasma. x. Inferior commissure (Guddeni) . 



inversely as the corpus callosum. Its importance diminishes with 

 the appearance of the corpus callosum in the lower mammalia 

 and it continues to decrease as the higher forms are approached. 

 Below mammals it is said to be the most important connecting 

 link between the hemispheres and is philogenetically very old. 



