DESTRUCTIVE LESIONS OF THE THALAMUS. 917 



" nerve " ; and from pulvinar pass fibres to the occipital and to the angular 

 regions of the cortex. 1 The lateral geniculate body also sends fibres to 

 the occipital cortex, including the borders of the calcarine fissure. 2 



In the lateral grey mass of the thalamus end many of the fibres of 

 the fillet ; they enter especially the ventral and posterior part of the 

 lateral mass, and lie around the median centre of Luys. Their region 

 there is known as the "field of the fillet." And it is from the lateral 

 grey mass of the thalamus that corticipetal fibres pass to the parietal 

 and falciform (mesial) regions of the cortex. From the front end of the 

 thalamus pass fibres to the frontal region of the cortex. A large and, 

 both phylogenetically and ontogenetically, early developed system of 

 fibres connects the thalamus with the corpus striatum. This in mam- 

 mals connects especially with the head of the nucleus caudatus ; but the 

 thalamus is also connected with the nucleus lenticularis (ansa lenticular is). 

 It also receives fibres from the superior cerebellar peduncle. 



Excitation of the thalamus. — Excitation of the thalamus by weak 

 faradisation produces little obvious result. 3 Ferrier 4 says : " I have not 

 observed any outward manifestation on irritation with a current sufficient to 

 excite active contraction when applied to the corpus striatum " ; except that, 

 in a monkey, when the electrodes were applied to the mesial surface near the 

 soft commissure, spasmodic extension of the legs resulted, and in a rabbit 

 movements of the eyes 5 and twitching of the opposite ear. These phenomena 

 might, he adds, " be regarded as indications of irritation of sensory centres." 



Destructive lesions and ablations of the thalamus. — Observers, 

 from Kolando, 6 Panizza, 7 and Eenzi 8 onwards, 9 have, after experimental 

 lesion of one thalamus, noted visual defect and dilatation of the contra- 

 lateral pupil, the latter a merely temporary symptom. The observation 

 by Hughlings Jackson 10 in 1875 of a case in which, post-mortem, a 

 softening of the right optic thalamus was discovered, confined to the pos- 

 terior part of the thalamus, and uncomplicated by destruction elsewhere, 

 was of fundamental assistance in indicating the functions of the thal- 

 amus. The symptoms observed were diminution of tactual sensibility on 

 the left side of the body, impairment of common sensitivity in the left 

 nostril, slight impairment of taste on the left side of the tongue, and of 

 hearing in the left ear, and loss of the left half of the field of vision of 

 each eye, i.e. blindness of the right half of each retina. Experimental 

 work on the subject thoroughly substantiates the teaching of this case. 11 



The defect of vision for the contralateral retina seems, at first at 



1 v. Monakow, " Gehirnpathologie," "Wien, 1897; and Arch. f. Psychiat., Berlin, 

 1888-92, Bde. xx. xxii. xxiv. ; Vialet, "Centres cerebraux de vision," Paris, 1893; 

 Ferrier and Turner, Phil. Trans., London, 1897. 



2 See especially Ferrier and Turner, ibid.; v. Monakow, op. cit. ; Henschen, "Klin. 

 Beitriige," Upsala, 1892. 



3 See for older literature in Eckhard, Hermann's "Handbueh," 1880, Bd. ii. Abth. 1. 



4 "Functions of the Brain," London, 1876, p. 161. 

 5 Topolanski, Arch. f. Ophth., 1898. 



6 "Saggio sopra il cervello," Sassari, 1809. 7 Loc. cit. 



8 " Saggio di iisiologia," Ann. univ. di mcd. e chir., Milano, 1860, p. 141. 



9 Lussana, " Monograiia d. Vertegine," Milano, 1872. 



10 London Hasp. Pep., 1875, vol. viii. 



11 Ferrier ("Functions of the Brain," 1876), Lemoine (These de Paris, 1880). Ferrier 

 and Ferrier and Turner (Phil, l^rans., London, loc. cit.), in the monkey, Lo Monaco (Arch, 

 ital. de biol., Turin, 1898, tomo xxx.), and Sellier and Vergier (Arch. dr. physio!, norm. 

 et path., Paris, Se>. 5, tome x. p. 706) in the dog, arrive at conclusions that, although 

 somewhat varying in detail, in the main harmonise with eacli other and the above. (See 

 also Fournie, " Recherches experimentales," Paris, 1873). 



