176 THE CEREBRAL HEMISPHERES. 



cribriform plate of the ethmoid bone to the olfactory mucous membrane, and on the 

 other hand into the glomeruli, where they ramify and form arborisations, which 

 interlace with those of the dendrites of the mitral cells. 



The relations of cells and fibres in the olfactory bulb have recently been reinvesti- 

 gated by Golgi, Ramon y Cajal, v. Gehuchten, and others, by the aid of Golgi's silver 

 nitrate method. The result of these investigations has been to show that the 

 olfactory nerve-fibres take their origin in the olfactory cells of the Schneiderian 

 membrane, which are therefore to be regarded as peripheral nerve-cells, and that 

 they terminate in the arborisations already mentioned as occurring in the olfactory 

 glomeruli. To these same glomeruli protoplasmic processes of the mitral cells also 

 pass and end in arborisations which intimately interlace with those of the olfactory 

 fibres. (Some of the protoplasmic processes of these cells do not, however, pass to 

 the glomeruli, but end in free arborisations in the deeper parts of the granule layer.) 

 On the other hand the axis-cylinder processes of the mitral cells pass upwards from 

 the rounded apex of the cell, and passing between the " granules " reach the white 

 fibres of the medullary ring. Turning sharply backwards nearly at a right angle 

 they then become continuous with the fibres of the ring (see fig. 127), ultimately 

 reaching the olfactory tract, along which they are conducted to the base of the 

 brain. As they pass upwards and also in their horizontal course, they give off 

 collateral fibres to adjacent parts of the bulb : these collaterals end after a shorter 

 or longer course in free arborisations in the grey matter. 



MEASUREMENTS OF THE BRAIN". 



Dimensions. The length of the cerebral hemispheres, measured from the 

 frontal to the occipital pole, varies in the larger proportion of cases between 160 mm. 

 and 170 mm. for the male brain ; and between 150 mm. and 160 mm. for the female 

 brain. The greatest transverse diameter of the whole brain for both sexes is about 

 140 mm. and the greatest vertical measurement of each hemisphere about 125 mm. 

 (Huschke). The brains of dolichocephalic individuals are naturally longer than 

 those of brachycephalic : in the latter there is a tendency to a breaking up of the 

 longitudinal gyri by transverse fissures, thereby increasing the amount of surface 

 and hence of grey cortex in proportion to the whole brain. 



Extent of grey cortex. The attempts hitherto made to measure or estimate the 

 relative proportions of the different convoluted parts of the cerebrum to each other 

 and to the degree of intelligence, either more directly or by the cranioscopic methods, 

 have been attended with little success. Such researches as those of Rudolph Wagner 

 give, however, some promise, when fully carried out, of affording more definite 

 results. These researches had for their object to institute an accurate comparison 

 between the brains of certain persons of known intelligence, cultivation, and 

 mental power, and those of persons of an ordinary or lower grade. As examples of 

 brains of men of superior intellect he selected those of Professor Gauss, a well-known 

 mathematician of eminence (aet. 78), and Professor Fuchs, a clinical teacher 

 (set. 52) ; and as examples of brains of ordinary persons, those of a woman of 29 

 and a workman. 



The careful measurement of all the convolutions and the intervening grooves in 

 the four brains above mentioned was carried out by H. Wagner, by covering the 

 cortex everywhere with gold-leaf, and determining the extent of surface by the 

 amount employed. The result of these measurements is partly given in the 

 accompanying table, the numbers indicating square millimeters of surface. 



It will be seen that although there are undoubtedly differences in the brains 

 examined, these are by no means so striking as might have been expected. Indeed 

 it may be stated that the general result of these and similar observations has been 



