46 Precentral or Motor Area [CHAP. 



In this case there was a repetition of the accompanying general cell disturbance, but 



the vascular alteration was not so obvious; again, also, the postcentral lamination was 



undisturbed, and, in the anterior direction, the changes did not transgress the Betz cell 

 boundary to any extent. 



SUMMARY. 



Summing up these observations, we see that in two typical cases of Amyotrophic Lateral 

 Sclerosis a thorough examination of the cerebral cortex has disclosed extremely interesting 

 and very remarkable changes, changes absolutely confined to the area over which the cells 

 of Betz are distributed, and consisting chiefly of a destruction and removal of the cells 

 named. In each case the general nature of the alteration was alike, both as regards the 

 severity of the destruction and its distribution ; only a few cells remained quite undisturbed, 

 at the lower end of the area, in the first case, while in the second, considerably more 

 untouched cells persisted and were found chiefly in the neighbourhood of the great annectant 

 gyrus. 



The concurrence of these remarkable alterations with clinical phenomena, pointing to an 

 affection of muscular and motor systems solely, is, in itself, a matter of great pathological 

 interest, and one which provides food for reflection on the pathology and especially on the 

 question of the starting point of the mischief which is at the bottom of this disease. In 

 an anatomical paper, however, it would be out of place to open a discussion on this question, 

 and we can well avoid it because from our standpoint, as students of localisation, it is more 

 interesting to find that these changes are absolutely limited to the area which recent 

 experimental and these histological researches point to as the correct motor area. Indeed, 

 I feel quite convinced that the facts disclosed by an examination of the brains in these 

 two cases can be held up as the strongest proof we can produce to the effect that in man, 

 as in the anthropoid ape, the motor area lies anterior to the fissure of Rolando, and that 

 we have been completely in error in believing that the postcentral gyrus shared the motor 

 function. Not least in importance is the point that these observations invest the position 

 held by the Betz cells as heads of the primary motor neurones with a definiteness and 

 security stronger than that offered by any previous observation. 



Although, with such definite results before us, it is a matter of slight moment that 

 others have stated that they have failed to find any cortical changes in cases of Amyotrophic 

 Lateral Sclerosis, I cannot refrain from expressing the opinion that that failure has been 

 due to lack of knowledge of the anatomical disposition of the true motor elements ; and if, 

 as is most probable, portions only of the cortex were looked into, the probability of a mis- 

 conception would be increased tenfold, because, in the first instance, one knows from one's 

 own experience how easy it is, in removing a portion of the precentral gyrus for section, 

 to miss the part containing motor elements, and secondly, in accordance with previous 

 doctrines, the integrity of cells in the postcentral gyri might readily have been mistaken 

 for normality of the motor zone ; and even if healthy Betz cells were found in isolated 

 localities it does not follow that this was their condition all over the field. Of course the 

 corollary is, that to obtain an accurate and convincing record of the cortical changes in such 

 cases, it is essential that the motor area be examined from end to end, and until by such 

 examination we derive a great deal more information than we at present possess, the results 

 of piecemeal work must be taken no notice of. 



