Till-: l-'C \CTHi.\AL AREAS OF THE CORTEX 869 



(3) The auditory (cochlear) area comprises the middle third of the superior temporal 



gyrus mid the transverse temporal gyri of the tempor:il i>|)errulum. Tin 1 motor port ion ot this 

 .-HIM lies in its inferior border. The fibres arising in the area course outwards in the temporal 

 pontile path to the motor nuclei of the medulla. 



(4) The olfactory area consist* of the olfactory tribune, the parolfactory area, the -\i\<- 

 callosal gyrus, part of the anterior perforated substance, the hippocainpiis (especially the um- 

 and the callosal half of the gyrus cjnguli. Its motor or efferent area lies chiefly in the hippo- 

 campal gyras, the lilires from which pass out from the telencephalon by way of the fornix. 



(.5) The gustatory area comprises the anterior portion of the fusiform gyrus and the zone 

 (motor portion) about the anterior extremity of the inferior temporal sulcus. 



(0) The association centres. The relatively lari.ce areas allotted at present to the so-called 

 higher psychic activities are indicated in fig. till. The great relative extent of these is one of 

 the characterisiics of the human brain. They probably merely represent the portions of the 

 cortex of which little is known, and may eventually be subdivided into more specific areas. They 

 are considered to be connected with the structures below by fewer projection fibres than are the 

 recognised sen "ned a!>o\e. while, on the other hand, they are rich in association fibres. 



Hy means of the latter they are in intimate connection with the specific areas and have abundant 



II of exercising a controlling influence upon the functions of these areas. According to 

 Flechsig, they consist of (1) a parirtnl tixxiicialion centre, comprising that part of the parietal 

 cortex between the somcesthetic area and the visual area; (2) an occijnto-lemporal association 

 i'1-ntrr, including the unspecified portions of the temporal lobe and the adjoining portion of the 

 occipital lobe not included in the visual area: (3) a frontal association centre, including all the 

 frontal lobe anterior to the spmsesthetic and olfactory areas. In the folds of the inferior parietal 

 lobule of the parietal association centre such intellectual activities as the optic discrimination 

 of words, letters, numbers, and objects generally are supposed to take place, while the superior 

 parietal lobule is the general region for the perception of form and solidity of objects the stere- 

 ognostic centre. To a portion of the middle temporal gyrus has been attributed the faculty of the 

 auditory discrimination of words and sounds ana the association of objects with their names. 



GENERAL SUMMARY OF SOME OF THE PRINCIPAL CONDUCTION 

 PATHS OF THE NERVOUS SYSTEM 



In the following summary the arabic numerals indicate paragraphs in which are mentioned 

 the nuclei or ganglia containing the cell-bodies of the neurones interposed in the chains; the 

 small letters indicate the different names given to the different levels of the pathways through 

 which their fibres run. For detailed descriptions of either nuclei or pathways see pages describing 

 them. Only the more common connections are mentioned here. 



I. THE CEREBRO-SPINAL PATH 



A. The ascending system of neurones. 



1. Spinal ganglion neurone of first order. 



(a) Terminal corpuscles and peripheral process of T-fibre. 



(b) Dorsal or afferent root of spinal nerve. 



(c) Ascending branch of bifurcation of dorsal root fibre in fasciculus gracilis, 



or fasciculus cuneatus of spinal cord. 



2. Nucleus of fasciculus gracilis or nucleus of fasciculus cuneatus in medulla oblongata 



neurone of second order. 

 (a) Internal arcuate fibres. 

 (6) Decussation of lemniscus. 



(c) Interolivary stratum of lemniscus of opposite side. 



(d) Medial lemniscus. 



3. Hypothalamic nucleus and lateral nucleus of thajamus neurone of third order. 



(a) Internal capsule, anterior part of its occipital portion. 



(b) Corona radiata, fronto-panetal part. 



(c) Somffisthetic area of cerebral cortex. 



B. Descending system of neurones (fig. 647). 



1. Giant pyramidal cells of soma-stlietic area. 



(a) Corona radiata, fronto-occipital part. 



(6) Internal capsule, genu and anterior part of occipital portion, 

 (c) Basis of the cerebral peduncle and the peduncle. 

 (</) Pyramid of medulla oblongata. 

 (e l ) Decussation of pyramids. 



(/') Lateral cerebro-spinal fasciculus (crossed pyramidal tract). 

 (e 2 ) Ventral cerebro-spinal fasciculus (direct or uncrossed pyramidal tract). 

 (f) Gradual decussation of latter in cervical and upper thoracic regions of spinal 

 cord. 



2. Cells of ventral horn of spinal cord of opposite side. 



(a) Ventral or efferent roots of spinal nerves. 



(6) Peripheral nerve-trunks directly to muscles or indirectly by way of sympathetic 

 neurones. 



II. SHORT 'REFLEX' PATHS OF SPINAL CORD 



1. Spinal ganglia. 



(a) Terminal 



(b) Dorsal root of spinal nerve. 



(a) Terminal corpuscles and peripheral process of T-fibre. 

 of s ' 



