392 MUSCULAR MOTION. 



ing forward with rapidity; but he does not back ; and frequently it is 

 impracticable to arrest his motion forwards. M. Magendie 1 asserts, that 

 he has opened several horses that died in this condition ; and found, in 

 all, a collection of fluid in the lateral ventricles, which had produced a 

 morbid change on the surface of the corpora striata, and must have 

 exerted a degree of compression on them. 



Similar pathological cases occur in man. M. Magendie relates the 

 case of a person, who became melancholic, and lost all power over his 

 movements ; continually executing the most irregular and fantastic 

 antics ; and frequently compelled to walk exclusively forwards or back- 

 wards until stopped by some obstacle. In this case, recovery occurred ; 

 and, accordingly, there was no opportunity for investigating the ence- 

 phalic cause. M. Itard describes two cases, in which the patients were 

 impelled, in paroxysms, to run straight forward, without the power of 

 changing their course, even when a river or precipice was before them. 

 A case is related by M. Piedagnel, 2 which is more to the purpose as an 

 opportunity occurred for post mortem examination. The subject of it 

 also was irresistibly impelled to constant motion. " At the time of the 

 greatest stupor," says M. Piedagnel, "he suddenly arose; walked 

 about in an agitated manner ; made several turns in his chamber, and 

 did not stop until fatigued. On another occasion, the room did not 

 satisfy him ; he went out, and walked as long as his strength would 

 permit. He remained out about two hours, and was brought back on a 

 litter." M. Piedagnel adds, "that he seemed impelled by an insur- 

 mountable force," which kept him in motion, until his powers failed 

 him. On dissection, several tubercles were found in the right cerebral 

 hemisphere, especially at- its anterior part ; and at the side of the cor- 

 pora striata. These had produced much morbid alteration in that hemi- 

 sphere ; and had, at the same time, greatly pressed on the other. From 

 these facts, M. Magendie infers it to be extremely probable, that, in 

 the mammalia and in man, a force of impulsion always exists, which 

 tends to impel backwards, and is, consequently, the antagonist to the 

 force seated in the cerebellum. 



3. Lateral Impulse. If the peduncles of the cerebellum crura 

 cerebelli be divided in a living animal, it immediately begins to turn 

 round, as if impelled by some considerable force. The rotation or cir- 

 cumgyration is made in the direction of the divided peduncle M. 

 Longet says, in the opposite direction and, at times, with such rapidity, 

 that the animal makes as many as sixty revolutions in a minute. The 

 same kind of effect is produced by any vertical section of the cerebellum, 

 which implicates from before to behind the whole substance of the me- 

 dullary arch formed by that organ above the fourth ventricle ; but the 

 movement is more rapid, the nearer the section is to the origin of the 

 peduncles ; in other words to their point of junction with the pons Varolii. 

 M. Magendie 3 affirms, that he has seen this movement continue eight 

 days without stopping, and apparently without any suffering. When 

 an impediment was placed in the way, the motion was arrested ; and, 



1 Op. cit., i. 338. 



2 Magendie, Journal de Physiologic, torn, iii.; and Precis Elementaire, i. 338. 



3 Precis, &c., i. 343. 



