LESIONS OF MESENCEPHALON. 913 



fore-limbs after destruction of the front part alone of the mesencephalon. 

 After transection through the posterior part of the region, pressure on 

 the foot often excites a crawling backward ; with the lobes intact it always 

 excites a spring forward. Circus movements and forced asymmetrical 

 postures frequently attend partial lesions. After transection behind 

 the mesencephalon, the cutaneous reflex time to Turck's stimulus (acid 

 water) is still abnormally long, though shorter than when the lobes are 

 stimulated, or the transection lies in front of mesencephalon. 1 



Kemoval of the mesencephalic roof in Testudo palustris induces 

 extraordinary activity. 2 The creature does not stumble against objects, 

 and evidently retains some visual power. The retraction of the head on 

 the shell being tapped, a normal reaction, drops out. When put into a 

 tank, instead of diving at once and hiding, the animal swims continually 

 at the surface. The ablation reduces the latent time for movement of 

 leg in response to stimulus of head from - 08 sec. to '05 sec, and the 

 liminal stimulus is lowered. 



In birds, destruction of one optic lobe impairs, 3 but does not com- 

 pletely destroy, the visual power of the contralateral eye. 4 Destruction 

 of an anterior corpus quadrigeminum abolishes 5 reflex contraction of the 

 pupil to light, " Whytt's reflex." c It is removal of the surface layer of 

 the lobes that seems to impair visual sensation, while it is the deeper 

 lesions which seem to most easily produce forced movements. Tran- 

 section, close in front of mesencephalon, leaves vocalisation fairly intact. 7 

 I found it still obtainable in the monkey, even after transection close 

 behind the anterior corpora ; transection behind the posterior bodies 

 seems to abolish it. The cry is a prolonged one, and in all the reflexes 

 obtained from the monkey (cat, dog, etc.), after transection at the front 

 limit of mesencephalon, there is a peculiar feature in regard to their time 

 character. 8 The reflex movements produced are executed with a curious 

 deliberate slowness, and the attitudes assumed are long maintained. It 

 has been concluded by Ziehen 9 that the tonic component of the epileptic 

 discharge into muscles is not cortical but subcortical. The " cataleptoid 

 reflexes," elicitable after transection at the mesencephalon, recall to 

 mind his conclusions. The state of constrained immobility, so-called 

 " hypnotic," into which many animals, e.g. frog, hen, can by skilled 

 handling be brought, has been shown by Verworn 10 to be accentuated 

 in decerebrate individuals. 



And it is after complete transection here that the condition 

 called decerebrate rigidity 11 supervenes. In this state the respiratory 



1 Setschenow, op. cit. 



2 Fano, "Contributo speriment. all. psicho fisiol. d. lobi ottici nel testuda palustre," 

 Reggio Emilia, 1886. 



3 Stefani, First Interna/. Cong. Physiol., Basle, 1889. 



4 Miinzer and Wiener, Monatschr. f. Psychiat. u. Neurol., Berlin, 1898, Bd. iii. S. 402 ; 

 Flourens, Renzi, etc., considered the blindness total. 



5 H. Mayo, " Anat. and Physiological Commentaries, " loc. cit., London, 1823 ; Flourens, 

 " Exper. sur le systeme nerveux," Paris, 1825 ; Budge, "Ueber d. Beweg. d. Iris," Braun- 

 schweig, 1855, S. 64. 



6 Robert Whytt, "Works," Edinburgh, 1768. 



7 Onodi, Berl. kiln. Wchnschr., 1894, S. 48. 



8 Sherrington, Proc. Roy. Soc. London, 1896, vol. lx. 



9 Arch. f. Psychiat., Berlin, 1887, Bd. xviii. 



10 " Beitr. z. Phys. d. Central nervensy stem," Jena, 1898 ; and Heubel, Arch. f. d. yes. 

 Physiol., Bonn, 1877, Bd. xiv. ; Danilewsky, ibid., 1881, Bd. xxiv. 



11 Sherrington, Proc. Roy. Soc. London, 1896, vol. lx. ; Lowenthal and Horsley, ibid., 

 1897, vol. lxi. ; Sherrington, Journ. Physiol., Cambridge and London, 1897, vol. xxii . ; 

 Phil. Trans., London, 1897. 



VOL. II. — 58 



