77^ THE CEREBRAL CORTEX. 



pyramidal tract which have been derived from the opposite pyramid of the 

 medulla oblongata (uncrossed lateral pyramidal fibres). And lastly, a certain 

 number remain in the anterior or ventral part of the cord, and are continued 

 down for a variable distance in the anterior column of the same side close 

 to the anterior median fissure (uncrossed ventral pyramidal fibres). This direct 

 or ventral pyramidal tract is not present as a distinct tract in the lower animals, 

 not even in monkeys ; l it is not known whether it occurs in the anthropoid 

 apes. The fibres of the lateral pyramidal tract terminate amongst the cells at 

 the base of the posterior horn, in the neighbourhood of the lateral horn, and 

 amongst the cells of Clarke's column, 2 not amongst the cells of the anterior 

 horn as has generally been assumed. 



Besides the connection with the lower centres, by means of the fibres 

 which the pyramids form, there appears to be another path of communication 

 between the motor cortex and the nuclei of the motor nerves, by way of fibres 

 which pass in the corona radiata and internal capsule to the nuclei of the 

 pons, and perhaps to the substantia nigra, and thence by fibres which go 

 either at once to the motor nuclei by way of the posterior longitudinal bundle 

 and anterior descending tract of the cord, or indirectly with intercalation of the 

 cerebellum. This second path of connection between the Rolandic area and 

 the lower centres has not, it is true, been absolutely proved, but its existence 

 would be very probable if the statement of Starbinger 3 is correct, that section 

 of the pyramids (in the dog) produces no persistent loss of voluntary power 

 over the muscles. 



Cajal 4 describes axons of many of the pyramidal cells of the frontal lobe 

 as passing to the corpus striatum. After destruction of the frontal lobe in 

 dogs and monkeys, Marinesco 5 found numerous degenerated fibres in the 

 corpus striatum and especially in the caudate nucleus. 6 On the other hand, the 

 corpus striatum receives numerous fibres from the thalanms and the sub- 

 thalamic region, and probably sends out centrifugal fibres downwards, along 

 the motor tract; but these have not hitherto been satisfactorily traced; some 

 appear to go to the substantia nigra. The corpus striatum is generally 

 believed to act as a centre for the higher reflex movements, and to be in close 

 association with the Rolandic area, but the experimental grounds for this 

 belief are still lacking. 7 Morphologically, the corpus striatum is regarded as 

 a part of the cortex. 



Corticipetal tracts pass, as shown by Flechsig, 8 to the Rolandic area 

 from the lateral nucleus of the thalamus (see p. 768). Monakow further found 

 that after extirpation of this part of the cortex in young animals, there was 

 atrophy in the fillet and in the nuclei of the opposite posterior columns of the 

 medulla oblongata. 9 Flechsig and Hosel 10 state that part of the fibres of the 



Berlin, 1893 ; Pitres, Arch, de physiol. norm, et path., Paris, 1894 ; Sherrington, Lancet, 

 London, 1894, vol. i. ; Mellus, Proc. Roy. Soc. London, 1894, vol. Iv. p. 208 ; and 1895, 

 vol. Iviii. p. 206 ; Boyce, Phil. Trans., London, 1895, B, p. 321 ; Redlich, Neurol. 

 Centralbl., Leipzig, 1897. 



1 Mellus (loc. cit.) occasionally found a few degenerated fibres in the anterior column of 

 the monkey, after lesions of the cortex. 



2 Schafer, "Proc. Phys. Soc.," March 18, 1899, Jonrn. PhysioL, Cambridge and 

 London, vol. xxiv. Of. Monakow, Arch. f. Psychiat., Berlin, 1895, Bd. xxvii. 



3 Jahrb.f. Psychiat., Berlin, 1896, Bd. xv. My own experiments on the monkey have 

 failed to confirm this statement. 



4 Cellule, Lierre et Louvain, 1892. 



5 Oompt. rend. Soc. de biol., Paris, 2 Fev. 1895. 



6 Cf. also on this subject H. Sachs, " Vortrage ii. d. Bau u. Thatigkeit d. Gehirns," 

 Breslau, 1893; Schukowski, Neurol. Centralbl., Leipzig, 1897, S. 524. 



7 Notlmagel, Virchow's Archiv, 1873, Bde. Ivii. and Iviii.; and 1874, Bd. Ix. ; 

 Kolliker, "Handbuch d. Gewebelehre," "Nervensystem," Leipzig, 1896, S. 622; Rezek, 

 Jahrb.f. Psychiat., Berlin, 1897, Bd. xvi. S. 40. 



8 "Die Localisation, u.s.w." 



9 See also v. Bechterew, "Leitungsbahnen," S. 158. 

 10 Neurol. Centralbl., Leipzig. 1890, No. 14. 



