ix] liitcnin'diatc Precentral Area 229 



lesion must be deep and penetrating. The explanation given for the occurrence of complete 

 and permanent motor aphasia after a deep-seated lesion in the pars basilaris is that all 

 connections between the "intermediate" cortex and the direct labial, lingual and laryngeal 

 centres occupying the lower end of the precentral area proper and by the way remaining 

 intact are severed. Such a lesion therefore produces an effect equivalent to destruction of 

 the whole of the " intermediate precentral " cortex coating the inferior frontal gyrus. 



9. In regard to agraphia it is interesting to find that those authorities who favour 

 the existence of a separate writing or cheirographic centre locate it at the base of the 

 middle frontal gyrus, exactly on a level with that part of the " precentral " cortex which 

 I have found altered in a case of amputation of the hand. 



10. From this and from what we know regarding motor aphasia it is inferred that 

 the " intermediate precentral " cortex harbours a sequence of centres for the control of skilled 

 movements, following the same order, deposited more or less on the same horizontal level, 

 and connected by commissural fibres with the series of " primary " centres existing in the 

 " precentral " area. 



11. As cells in the "intermediate precentral" area may control higher evolutionary move- 

 ments, so the Betz cells may govern primary automatic movements. That the oro-lingual and 

 laryngeal muscles are left unparalysed when speech is abolished is significant in this respect. 

 The disparity in number of Betz cells in the arm and leg areas of the human brain 

 is also hard to explain unless on these grounds, and it is probable that the disparity is 

 not maintained in quadrupeds. 



12. It is surmised that the automatic movements of which the lower animals are alone 

 capable are directly actuated by the equivalents of Betz cells, and from the phylogenetic 

 point of view such cells are probably of great age. 



REFERENCES. 



EBEUSTALLER. Das Stirnhirn. Leipzig, 1890. 



WALDEYER. Das Gibbon-Hirn. Quoted by Cunningham. 



CUNNINGHAM. Loc. cit. 



ELLIOT SMITH. Catalogue of the Royal College of Surgeons' Museum. London, 1902. 



HERVE. La circonvolution de Broca. Paris, 1888. 



GRATIOLET. Quoted by Cunningham. 



J. HUGHLINOS JACKSON. On Convulsive Seizures. Lumleian Lectures, delivered before the Royal 

 College of Physicians of London. British Medical Journal, Vol. I, 1890 ; and other papers. 



BEEVOR and HORSLEY. A Record of the Results obtained by Electrical Excitation of the so-called 

 Motor Cortex and Internal Capsule in the Orang-Outang (Simia Satyrus). Phil. Trans. Roy. 

 Soc., Vol. CLXXI, B. London, 1890. 



P. FLECHSIG. Loc. cit. 

 VON MONAKOW. Loc. cit. 



