ORIGIN OF THE CEREBRAL NERVES. 495 



reaches nearly as far as the lower border of the pons, measuring 

 in a transverse direction 1/6 millimeters, and in the antero- 

 posterior diameter 2*4 millimeters. 



This nucleus lies just on the outer side of the superior olivary 

 body, and appears sharply defined in Man (fig. 254, on the left 

 side, 7), through the curvatures of a nuclear tract or convolution 

 (Knauel) in which the fasciculi of origin are imbedded, the 

 central extremities of which may connect the nucleus through 

 the raphe with the crus cerebri. The nucleus, as a whole, is 

 less sharply defined in animals, because the convolutions of 

 which it is composed, are, like those in the glomeruli olfactorii, 

 separated from each other by connective tissue (fig. 255, 7). The 

 peripherically running fibres of the glomerulus run separately, 

 and in small groups, forming a curve directed outwards as far 

 as to the grey floor, and there collect into a geniculate compact 

 fasciculus, with its convexity looking upwards the facial genu 

 of Deiters which during its course of 5 millimeters occurs in 

 all transverse sections to the inner side of and behind the root 

 of the abducens, its nucleus appearing as a dark sharply defined 

 area (fig. 254, on the left side, &). The genu, therefore, appears 

 to be separated from the emerging root of the facial by these two 

 structures, because it is continuous with the latter, by means of 

 an arch (that curves over the facialis-abducens nucleus), and is 

 consequently cut off at the crown. The ascending root of the 

 facial repeats at its exit, about 5 millimeters higher up, the ex- 

 ternally convex curve described by its fasciculi on leaving their 

 nucleus (fig. 254, G 7, on the right side). Since the emerging 

 roots of the facial spread themselves through a portion of the 

 pons, measuring about 2 millimeters in height, their inferior 

 fasciculi, it is obvious, must, in a series of transverse sections, 

 be situated opposite to the geniculate portion (fig. 254, on the 

 left side). 



The ascending roots of the facial consequently form a fasci- 

 culus unconnected with the abducens nucleus, but which 

 diverges to make way for this nucleus and the root of the 

 abducens, and curves round them in the form of a horseshoe. 

 The crura of this horseshoe lie in the pons superjacent and 

 parallel to one another; the inferior crus conducts inwards 

 and backwards to the genu the fasciculi proceeding from the 



