690 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



origin of the third pair of cerebral nerves in the gray matter around the aqueduct of 

 Sylvius to the nucleus of origin of the lowermost coccygeal nerve of the spinal cord. 



Speaking generally, the cortex of the cerebrum presents five laminae (Fig. 1'45). 

 The first is principally composed of an equally punctated matrix, with a few small 

 stellate cells, and near its surface numerous fine varicose nerve-fibres decussating in 

 all directions. The matrix Meynert considers to consist chiefly of a non-nervous 

 substance. It has been called ependyma formation by Kokitansky, neuroglia by 

 Virchow. connective tissue by Kolliker, coalesced ganglion cell-substance bv lienle 

 and R. Wagner, gelatinous substance by Clarke, and molecular substance bv Kupfer. 

 The second is a layer of close-set, small pyramidal corpuscles; the third is a layer 

 of large pyramidal corpuscles; the fourth is a layer of small, close-set, irregular- 

 shaped corpuscles; and the fifth is a layer of fusiform corpuscles. 



FIG. 244. 



FIG 245. 



CJt 



-TeffiaenHum 



..(Suit, are/. 



FIG. 244. CCJf, Cortex of the cerebral hemispheres, the convolutions of which are seen to be con- 

 nected by arcuate connecting fibres. Cb, Cortex of cerebellum. CR, Corona railiata, consisting of 

 fibres extending from (lie cortex ccrcbri to Z/JVand CA', the lenticular and caudate nuclei ol' (be corpus 

 striatum, and to OT, the optic thalamus. The posterior extremity of the optic thalamus presents two 

 enlargements, the corpus geniculatum cxternum and iiitcriuiin, which is seen to be connected with 

 I be optic tracts. The letters Op. Tr. arc placed on a band of fibres that arc believed to run directly 

 from the cortex cerebri to the cortex cerebelli. W, Stria cornea, or tienia scmicircularis. A'.V, Red 

 nucleus nf tegmenttim. A r , Nates. T, Test is. P, Pineal gland, b, Fibres passing directly into the 

 tegmcntnm from the cortex cerebri. Pa C, The band of fibres to the right of these letters are part of 

 the superior peduncle of the cerebellum. 



Fin. 215. Transparent section of a furrow of the third central convolution of Man, X 100 diain. 

 1. Layer of scattered small cortical corpuscles. 2. Layer of close-set, small pyramidal, cortical cor- 

 puscles. :;. Luyer of large pyramidal corpuscles. 4. Layer of small, close-set, irregularly shaped, 

 corlical corpuscles (granule-like formation). 5. Layer of fusiform cortical corpuscles, in, -Medullary 

 layer. 



The different parts of the same hemisphere are connected, first, by the numerous 

 intercommunicating processes of the cells; and, secondly, by a system of arcuate 

 fibres of different lengths lying immediately beneath the cortex. The corresponding 



