1906-7.] Experimental Lesions in Motor Cortex of Monkey. 283 
tracts the longer fibres tend to occupy a more peripheral position, the 
shorter fibres to lie nearer to the grey matter. Flatau* * * § (1897) and 
others have found that a similar arrangement obtains both for the spino- 
cephalic and for the longitudinal commissural fibres terminating in 
the grey matter and uniting the different segments of the cord to one 
another ; those fibres which unite adjacent segments lie close to the grey 
matter, while those passing between more distant segments are situated 
nearer to the periphery of the cord. Sherrington and Laslett,j* again, in 
1903 showed that the fibres of the direct cerebellar tract of Flechsig are 
arranged in definite strata, those from the post-thoracic region of the cord 
lying outermost, those of most anterior origin lying innermost, and fibres 
of intermediate origin forming intermediate strata. 
In view of the observations above recorded (and many more are to 
be found in the literature corroborative of these), it might naturally be 
supposed that the same arrangement would be found in the fibres of the 
descending tracts of the spinal cord, particularly in the pyramidal tract, 
the largest and most important of these, and it has been stated by Gad 
and Flatau J that such is the case. These observers, adopting the direct 
excitation method, such as was employed by Beevor and Horsley in 
the case of the internal capsule, divided the cord transversely in the 
cervical region below the origin of the phrenics, and stimulated with 
the faradic current the freshly made cross section of the caudal portion 
within the area of the crossed pyramidal tract. They used in their 
experiments large dogs. They came to the general conclusion that the 
fibres innervating the forelimbs and upper segments of the body lie 
nearer to the grey matter than those which supply the hindlimbs 
and lower segments. This would appear to agree with the above-men- 
tioned law for the ascending and internuncial fibres of the cord, viz., that 
the short fibres run nearer the grey matter, the long fibres nearer the 
periphery. 
Ziehen § is quoted by them as having come to a somewhat different con- 
clusion by the degeneration method. In dogs which had been operated 
on by H. Munk, he found that after extirpation of limited portions of the 
motor cortex the degenerated fibres from the forelimb area in the upper 
cervical region lay nearer the grey matter, while those from the neck 
area were placed outside them, nearer the periphery. There was differentia- 
* Flatau, Sitz. der Jconigl. preuss. Akad. d. Wissen. zu Berlin , 1897. 
t Sherrington and Laslett, Jour, of Physiol., vol. xxix. (1903), p. 191. 
+ Gad and Flatau, Neur. Gent., 1897, p. 481. 
§ Ziehen, Archiv f. Psychiat ., 1887, p. 300. 
