710 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



the animal usually remains in a state of profound stupor, although still retaining 

 the erect position ; and it is only when irritated by pinching or pricking, that it 

 will execute any rapid movements. No mechanical irritation of the Corpora 

 Striata produces either signs of pain or muscular movement. No distinct evi- 

 dence regarding the special functions of either of these ganglionic masses can be 

 gained from Pathological phenomena. So far as is yet known, extensive disease 

 of either the Thalamus Opticus or the Corpus Striatum of one side produces 

 hemiplegia, or paralysis both of sensation and motion, on the opposite side. 

 The same result very commonly follows an apoplectic effusion into the substance 

 of either; and although it has been maintained that, when the lesion is limited 

 to the Corpus Striatum, the posterior member is peculiarly or alone affected, and 

 that lesion of the Thalamus Opticus alone has a special tendency to occasion 

 paralysis of the anterior member, yet the careful analysis which has been made 

 by Andral 1 into the pathological phenomena afforded by seventy-five cases of 

 paralysis in which the apoplectic effusion was limited to one or other of these 

 bodies, does not afford the least countenance to any such doctrine. And it is 

 affirmed by Longet, that injury or removal of the Corpus Striatum of one side 

 did not, in his experiments, affect the posterior more than the anterior limb ; 

 nor could he detect any difference in the condition of these limbs after the re- 

 moval of the Thalamus. 



738. When the fibrous tracts which connect these ganglionic masses with the 

 Medulla Oblongata, and which are commonly (but erroneously) designated as 

 the Orura Cerebri, are completely divided, the result, as might be anticipated, 

 is the annihilation of sensibility and of the power of voluntary movement in the 

 body generally. 3 When, however, the Crura Cerebri of a rabbit are not com- 

 pletely divided, but one of them is partially cut through, a little in front of the 

 Pons Varolii, the animal is said by Longet and Schiff to exhibit a constant 

 tendency to turn towards the side opposite to that of the lesion, so that it per- 

 forms the circular evolution du maneye ; the diameter of its circle of movement 

 being smaller, in proportion as the incision approaches the edge of the Pons. 

 But if one of the Crura be completely divided, the animal then falls over on 

 the opposite side ; the limbs of that side being paralyzed to the influence of the 

 Encephalic centres, though they may be still caused to exhibit reflex motions. 

 Hence it appears that the circular movements which are performed after incom- 

 plete lesions of the Crus Cerebri and Thalamus Opticus of either side, are due 

 to the weakening of the sensori-motor apparatus of the opposite side, whereby 

 the balance of the muscular actions of the two sides is destroyed. Nearly the 

 same results have been obtained on this point by Longet, Lafargue, and Schiff. 

 Considerable importance is attached by some Physiologists to the part of the 

 Encephalon known as the Tuber Annulare, to which the name of Mesocephale 

 has also been given. This is not altogether synonymous with the Pons Varolii, 

 as some Anatomists have represented it; for, while the latter consists of trans- 

 verse fibres, which form the commissure between the hemispheres of the Cere- 

 bellum, surrounding and passing between the longitudinal fibres of the Sensory 

 and Motor tracts which constitute the Crura Cerebri, the Tuber Annulare (which 

 exists in animals whose Cerebellum has no hemispheres) is a projection from 

 the surface of the proper Medulla Oblongata, containing a considerable nucleus 

 of vesicular matter. The experiments of Longet have led him to the conclusion 



1 "Clinique Medicale," torn. ii. p. 664, et seq. 



2 It is considered by Longet that these functions are not completely destroyed, because 

 the animals on whom this operation has been performed still retain some power of move- 

 ment, and respond by cries to impressions that ordinarily produce pain. There is no proof, 

 however, that such actions are other than "excito-motor;" they certainly cannot in them- 

 selves be admitted as proving the persistence of consciousness in the lower segment of the 

 Cerebro-Spinal axis. 



