7 20 CORPORA QUADRIGEMINA. 



half of one side of the pons, the facial paralysis is on the same side as the paralysis of the body. 

 But the parts supplied by the 5th and 6th nerves may also be involved. This is explained by 

 fig. 504, where the upper facial fibres cross in the pons. Sudden and extensive lesions of the 

 pons are frequentlv associated with hyperpyrexia, the temperature often rising rapidly within 

 an hour, perhaps "from the grey matter in the floor of the 4th ventricle being affected ; but 

 whether'it is due to some effect on a heat-regulating or heat-producing centre is uncertain. 

 Tumours of considerable size may press on the pons without producing very marked symptoms, 

 as tumours tend to push aside tissues, unless they be infiltrating in their character. Lesions of 

 the transverse superficial fibres (middle cerebellar peduncles) often give rise to involuntary 

 forced movements, there being a tendency to move to one side or the other.] 



The Corpora Quadrigemina. Destruction of these bodies on one side in 

 mammals (or their homologues, the optic lobes in birds, amphibians, and fishes) 

 causes actual blindness, which may be on the same or the opposite side, according 

 to the relation of the fibres crossing at the optic chiasma ( 344). Total destruction 

 causes blindness of both eyes. At the same time, the reflex contraction of the 

 pupil, due to stimulation of the retina with light, no longer takes place {Flourens), 

 where the optic is the afferent and the oculomotorius the efferent nerve ( 345). 

 If the cerebral hemispheres alone be removed, the pupil still contracts to light, as 

 well as after mechanical stimulation of the optic nerve (H. Mayo). Destruction of 

 the corpora quadrigemina interferes with the complete harmony of the motor acts ; 

 disturbance of equilibrium and inco-ordination of movements occur (Serves). In 

 frogs, Goltz observed not only awkward clumsy movements, but at the same 

 time the animals have to a large extent lost the power of completely balancing the 

 body (p. 683). A similar result was observed in pigeons (M'Kendrick) and 

 rabbits (Ferrier). Extirpation of the eyeball is followed by atrophy of the opposite 

 anterior corpus quadrigeminum (Gudden). 



According to Bechterew, the fibres of one optic tract pass through the anterior brachium (fig. 

 500) into the anterior pair (nates) of the corpora quadrigemina ; while those fibres which cross 

 in the chiasma (fig. 425) pass into the posterior pair (testes). According to this arrangement 

 we have partial blindness, according as one or other pair of these bodies is destroyed. 



[In man, very little is known regarding the effects of disease of the corpora quadrigemina, 

 interference with the ocular muscles being the most marked symptom ; but the inco-ordination 

 of movement which has been observed may be due to pressure upon the superior cerebellar 

 peduncle, while it is by no means certain that the defects of vision are directly due to lesions of 

 these bodies.] 



Stimulation of the Corpora Quadrigemina. The corpora quadrigemina react to electrical, 

 chemical, and mechanical stimuli. The results of stimulation are very variously stated. 

 According to some observers, there is dilatation of the pupil, on the same side ; according to 

 Ferrier, it may be the pupil on the opposite or on the same side. The stimulation may 

 be conducted from the corpora quadrigemina to the medulla oblongata, and to the origin of the 

 sympathetic, for, after section of the sympathetic nerve in the neck, dilatation of the pupil no 

 longer takes place. According to Knoll, the contraction of the pupil observed by the older 

 xiHTimenters occurs only when the adjoining optic tract is stimulated. Stimulation of the 

 right anterior corpus quadrigeminum causes deviation of both eyes to the left (and conversely) ; 

 on continuing the stimulation, the head is turned to this side. On dividing the corpora quad- 

 rigemina by a vertical median incision, stimulation of one side causes the result to take place 

 only on one side {Adamtik). Ferrier observed signs of pain on stimulating these organs in 

 mammals. Carville and Duret conclude from their experiments, that these organs are centres 

 for the extensor movements of the trunk. Ferrier found, on stimulating one optic lobe in a 

 pigeon, dilatation of the opposite pupil, turning of the head towards the other side and back- 

 wards, movement of the opposite wing and leg ; strong stimulation caused flapping movements 

 of both wings. Danilewsky, Ferrier, and Lauder Brunton observed a rise of the blood-pressure 

 and slowing of the heart-beat, together with deeper inspiration and expiration. 



Bechterew ascribes all the phenomena, except those of vision itself, which accompany injury 

 or stimulation of these bodies, to affections of deeper seated parts. He asserts that the corpora 

 quadrigemina contain neither the centre for the movements of the pupils nor that for the 

 combined movements of the eyeballs ; not even the centre for maintaining the equilibrium of 

 the body. Stimulation of these bodies causes the animals to perform marked movements. 

 Reflex phenomena, nystagmus, forced movements, and unsteadiness of the gait only occur, 

 however, when the deeper parts are injured. 



Pathological. Lesions of the anterior pair in man, according to the extent of the lesion, 

 cause disturbance of vision, failure of the pupil to contract to light, and even blindness ; there 



