THE HYPOGLOSSAL. 



577 



Fig. 182. 



Kolliker regards the roots of the hypoglossal nerves as decussating 

 completely with each other through the raphe, at the level of the nuclei. 

 According to both Clarke and 

 Dean, on the other hand, a 

 portion of the fibres of each 

 root terminate in the corre- 

 sponding nucleus, while an- 

 other portion bend inward 

 and cross the raphe at the 

 median line, decussating with 

 those of the opposite side, 

 Henle describes a few thin 

 bundles of fibres which con- 

 nect the roots of the nerve on 

 each side, at their point of 

 emergence, with the raphe in 

 front of the medulla. It is 



certain that the hypoglossal, 

 like the other cranial nerves, 



xn 



TRANSVERSE SECTION ov THE HTTMA.N 

 MEDULLA OBLONGATA, through the olivary 

 nucleus and root of the hypoglossal nerve. A p. 

 Anterior pyramid. XII. Hypoglossal nerve roor. 

 Magnified 8 diameters. (Henle.) 



has, in some way, a connec- 

 tion with the opposite side of 

 the brain ; since cases of facial 

 paralysis from cerebral hemor- 

 rhage are often accompanied by paralysis of the tongue on the same 

 side with that of the face, and on the opposite side to that of the lesion. 

 One of the genio-hyo-glossal muscles having lost its power, while the 

 other remains active, if the patient attempts to protrude the tongue in 

 such cases, its point is deviated toward the paralyzed side. 



After leaving the anterior surface of the medulla oblorigata the fibres 

 of the hypoglossal nerve become parallel with each other, and, passing 

 through the anterior condyloid foramen of the occipital bone, emerge 

 from the skull in the form of a cylindrical cord. Immediately after 

 escaping from the condyloid foramen it presents one or two branches 

 of inosculation with the pneumogastric, at the point where it crosses the 

 track of this nerve. According to Cruveilhier, the dissection of the parts, 

 after maceration in dilute nitric acid, shows distinctly that this inoscula- 

 tion consists of fibres which leave the hypoglossal nerve and join those 

 of the pneumogastric, running with them in a peripheral direction. The 

 hypoglossal nerve then passes downward, nearly to the level of the hyoid 

 bone, where it curves forward, giving filaments to the styloglossal and 

 hyoglossal muscles, and to those immediately beneath the hyoid bone; 

 after which it turns upward, penetrates the tongue from below, inoscu- 

 lates by two or three filaments with the lingual branch of the fifth pair, 

 and is finally distributed to all the muscles of the substance of the 

 tongue. It, therefore, animates not only the lingual muscles proper, 

 but also those which draw the tongue backward and upward (stylo- 

 glossal), and backward and downward (hyoglossal and infra-hyoid mus- 



