806 FORCED MOVEMENTS. 



quadri geminate bodies to the medulla oblongata and further on to the origin 

 of the sympathetic, for after section of the cervical sympathetic the dilatation 

 no longer takes place. According to Knoll contraction of the pupil, such as was 

 observed by earlier investigators, takes place only when the adjacent optic-nerve 

 tract is irritated. In addition, irritation of the right anterior quadri geminate 

 body causes rotation of both eyes to the left, and conversely. If the irritation 

 be continued the head also is rotated toward the same side. Vertical section of 

 the quadrigeminate bodies in the median line is followed, on unilateral irritation, 

 by this result only upon the same side. Ferrier observed, further, signs of pain 

 on irritation of the quadrigeminate bodies in mammals. Danilewsky, Ferrier, 

 and Lauder Brunton observed, finally, increase in blood-pressure and slowing of 

 the heart-beat, together with deep respirations. 



Bechterew attributes all of the phenomena that occur after injury or irritation 

 of the quadrigeminate bodies, except those referable to vision itself, to lesions 

 of more deeply situated parts. Therefore, according to him, the quadrigeminate 

 bodies themselves contain neither the center for the movements of the pupils nor 

 that for the combined movements of the eyes, nor do they contain that for main- 

 taining the equilibrium of the body. Irritation of the quadrigeminate body causes 

 the animals to start back markedly as a reflex phenomenon. Nystagmus, forced 

 movements, and uncertainty in walking occur also only in association with 

 injuries of more deeply situated parts. 



Pathological. Lesions of the anterior quadrigeminate bodies in man give rise, 

 in accordance with their extent, to visual disturbances, immobility of the pupils and 

 even blindness. In addition profound injury may be attended with paralysis of 

 the oculomotor nerves on both sides, in consequence of which the affected ocular 

 muscles are not involved with entire symmetry and not in equal degree. An un- 

 certain staggering gait, especially if it appears as the first symptom, is likewise 

 characteristic. 



Destruction of the posterior commissure in rabbits has the same effect as 

 section of both oculomotor nerves; a lesion causes only diminution in the irrita- 

 bility of these nerves. An incomplete asymmetrical lesion causes asymmetrical 

 diminution in the irritability of the two nerves, the nerve upon the side of the 

 lesion being less irritable than that upon the opposite side. 



Forced Movements. The significance of the midbrain in relation to 

 the harmonious execution of movements makes it clear that unilateral 

 injuries of such parts as are connected with it by means of conducting 

 fibers cause peculiar unilateral disturbances of equilibrium and devia- 

 tions from the symmetrical movements of both sides of the body that 

 have been designated forced movements. In this category belong the 

 circular movement (mouvement de manege), in which the animal, with 

 the intention of running onward, moves constantly in a circle; the index- 

 movement, in which the fore part of the body is moved about the station- 

 ary posterior part, like an indicator about its axis; the rolling movement, 

 by means of which the body is revolved about its longitudinal axis. All 

 of these forms of movement may pass into one another, and they rep- 

 resent only gradual variations in the same disorder. The parts injury 

 of which causes these forced movements are the striate body, the optic 

 thalamus, the cerebral peduncle, the pons, the middle cerebellar pedun- 

 cle, certain portions of the medulla; and even after injury of the surface 

 of the cerebrum Eulenburg and Landois observed index-movements in 

 rabbits, and Bechterew in dogs. Also in man forced movements have been 

 observed, especially in association with lesions of the parietal convolu- 

 tions. Forced movements, together with nystagmus and rotation of the 

 eyes, are caused also by injury to the olive. 



On pathological degeneration of one olive of the medulla oblongata pronounced 

 rotatory movements toward the same side have been observed in man. 



Statements differ as to the direction and the character of the movements 

 after the individual injuries. The following observations have been made: Sec- 

 tion of the anterior portion of the pons and the cerebellar peduncles causes 



