FUNCTIONS OF THE BRAIN. 59 



contrary, conceive of the ' motor zone ' as essentially sen- 

 sory, and in different ways explain the motor disorders as 

 secondary results of the anaesthesia which is always there, 

 Muuk calls the motor zone the Fiihlsphiire of the animal's 

 limbs, etc., and makes it coordinate with the Sehsphare, 

 the Hursphiire, etc., the entire cortex being, according to 

 him, nothing but a projection-surface for sensations, with 

 no exclusively or essentially motor part. Such a view 

 would be important if true, through its bearings on the 

 psychology of volition. What is the truth? As regards 

 the fact of cutaneous anaesthesia from motor-zone ablations, 

 all other observers are against Ferrier, so that he is proba- 

 bly wrong in denying it. On the other hand, Munk and 

 Schiff are wrong in making the motor symptoms depend on 

 the anaesthesia, for in certain rare cases they have been 

 observed to exist not only without insensibilitj-, but with 

 actual hypersesthesia of the parts.* The motor and 

 sensory symptoms seem, therefore, to be independent 

 variables. 



In monkeys the latest experiments are those of Horsley 

 and Schaefer,f whose results Ferrier accepts. They find 

 that excision of the hippocampal convolution produces tran- 

 sient insensibility of the opposite side of the body, and that 

 permanent insensibility is produced by destruction of its 

 continuation upwards above the corpus callosum, the so- 

 called gyrus fornicatus (the part just below the * calloso- 

 marginal fissure ' in Fig. 7). The insensibility is at its maxi- 

 mum when the entire tract comprising both convolutions is 

 destroyed. Ferrier says that the sensibility of monkeys is 

 'entirely unaft'ected' by ablations of the motor zone,:}: and 

 Horsley and Schaefer consider it by no means necessarily 



*Bechterew (Pflliger's Archiv., vol. 35, p. 137) found no anaesthesia in 

 a cat with motor sj^mptoms from ablation of sigmoid gyrus. Luciani got 

 hyperaesthesia coexistent with cortical motor defect in a dog, by simulta- 

 neously hemisecting the spinal cord (Luciani u. Seppili, op. cit. p. 234). 

 Goltz frequently found hj-persesthesia of the whole body to accompany 

 motor defect after ablation of both frontal lobes, and he once found it 

 after ablating the motor zone (Pfluger's Archiv, vol. 34, p. 471). 



f Philos. Transactions, vol. 179, p. 20 ff. 



X Functions, p. 375. 



