224 Motor Aphasia [CHAP. 



area indicated, and leaving the lower end of the ascending frontal convolution intact, would 

 be an anatomical rarity; a case of localised meningitis might supply the needed condition, but 

 the arterial supply of the parts is such that we could not expect it from a case of occlusion by 

 thrombosis or embolism, or from a haemorrhage. 



Also experiment is silent on the question. The region has been carefully explored by 

 Sherrington and Grimbaum in the anthropoid ape, and they state that "faradisation of the 

 cortex of the inferior frontal convolution has failed so far to elicit movements of any satisfactory 

 degree of regularity or constancy; and this even under use of currents much stronger than 

 those which suffice when applied to the 'motor' cortex proper. From the posterior region 

 of the convolution, at scattered points, and without constancy even at them, strong faradisation 

 occasionally seemed to induce movements in the larynx, distinguishable from the rhythmic 

 of respiratory origin." And they conclude "that either (1) no Broca 'speech centre' at all 

 foreshadowing the human exists in these brains, or (2) that direct faradisation of the Broca 

 speech cortex is inefficient in itself to evoke vocalisation." 



These results are disappointing, for although speech is denied them it seems right to 

 suppose that the vocal sounds which the ape is capable of uttering, and indeed likewise many 

 of the calls and cries of other vertebrates lower in the scale, are to them as speech is to the 

 human lii-ing, and that the nervous mechanism concerned in their production is of a kindred 

 nature. Reasoning therefore by analogy, I would certainly anticipate that stimulation by 

 strong currents, not by weak ones, would produce laryngeal or even oral and lingual movements 

 suggestive of vocalisation when applied to the lower part of the " intermediate precentral " 

 area ; and with reference to Sherrington and Griinbaum's statement that suggestive movements 

 of the vocal cords were obtained at scattered points in the lower frontal gyrus, I shall be 

 interested to read further details in their full paper : because, as I have mentioned previously, 

 the distribution of this cortex in the manlike ape is very peculiar in the preinsular region, 

 and if histology is a reliable guide, I would expect to find only that curiously distributed strip 

 of cortex excitable, which I believe to be the homologue of the " intermediate precentral " cortex 

 in man ; from all that exposed cortex specially referred to as really pertaining to the insula, no 

 result would be anticipated. 



Bearing in mind that psychical components exercise a still higher control over the speech 

 area, not to mention tbe exceedingly complex nature of the motor mechanism, it is impossible 

 to imagine how physical stimulation of the human speech area at a single point could be 

 productive of vocalisation ; isolated laryngeal, lingual, or labial movements might follow, 

 perhaps, but nothing further. 



And this leads up to another question bearing on speech which seems worthy of mention, 

 but upon which lack of evidence prevents discussion. It is whether there is any possibility 

 of effecting a further subdivision of the speech area, whether the elements in the " intermediate 

 precentral" area for the higher control of the respective primary oral, labial, lingual and 

 laryngeal elements in the " precentral " area, are like the latter deposited in separate com- 

 partments, and whether in course of time we shall be able to point to a given subdivision 

 of this area and say that its destruction would, for instance, be followed by an inability to 

 pronounce labials, and so on. To my mind the anticipation is rational. 



