440 



NA rURE 



IMarck lo, 1887 



which he has since seen reason to introduce in the 

 original scheme, and the resiiUs which have been arrived 

 at by certain otlier worliers in this field of research. 



Fig. 1 is a diagram of the outer surface of the left 

 hemisphere of the monkey's brain : in it the fissures are 

 represented by black lines. It is seen to be crossed 

 obliquely by six prominent fissures (besides less important 



depressions). These, enumerated from before back, are 

 the pre-central, Rolandic, intra-parietal, Sylvian, parallel, 

 and parieto-occipital fissures. The anterior portion of 

 the hemisphere in front of the pre-central fissure is 

 termed the prefrontal lobe. The part of the brain behind 

 this, and bounded behind by the intra-parietal and Sylvian 

 fissures, may be designated the Rolandic region, since it 

 includes the Rolandic fissure. The next part, posteriorly, 

 lies in the angle between the intra-parietal and parieto- 

 occipital fissures, and has the end of the parallel fissure 

 running up into it : it is known as the angular gyrus. 

 Behind the parieto-occipital fissure is the occipital lobe. 

 The rest of this surface of the hemisphere below and 

 behind the Sylvian fissure is the temporo-sphenoidal 

 lobe : the convolution in this which lies between the 

 Sylvian and the parallel fissures, and which is thus very 

 well marked off from the rest of the lobe, is the superior 

 temporo-sphenoidal gyrus. 



Fig. 2 represents the mesial and under surface of the 

 left hemisphere. We here see, above the cut corpus 

 callosum and the other parts which unite the two hemi- 

 spheres, two convolutions running longitudinally, and 

 separated by a well-marked fissure, the calloso-ma'rginal. 

 The upper one is termed the marginal gyrus, the lower 

 the gyrus fornicatus. The latter expands posteriorly into 



the quadrate lobule, and is then continued around the 

 posterior end of the corpus callosum on to the under 

 surface of the temporo-sphenoidal lobe, where it becomes 

 continuous with the hippocampal gyrus. The internal 

 parieto-occipital fissure, continuous above with the exter- 

 nal one of the same denomination, cuts off, like that, the 

 occipital lobe from the rest of the brain. 



Briefly stated, the positions taken up by Dr. Ferrier in 

 the first edition of tliis work were as follows : — 



(i) The Rolandic region is motor. This is the part of 

 the hemisphere from which all volitional impulses (at 

 least for the limbs, head, and face, — about the trunk- 

 muscles nothing was ascertained) issue. It is not con- 

 nected with sensory perceptions of any kind, not even 

 with those of the muscular sense. 



Evidence. — Electric excitation in this region in animals 

 produces definite and co-ordinated movements of muscles 

 of the limbs, neck, and face, similar to those which occur 

 in voluntary efforts. Extirpation is followed by imme- 

 diate and permanent paralysis of those muscles without 

 the occurrence of any loss or impairment of sensation in 

 the corresponding parts. 



(2) The angular gyrus is the centre for vision with the 

 opposite eye. 



Evidence. — Electric excitation of this convolution pro- 

 duces movements of the eyes towards the opposite side, 

 contraction of the pupils, and closure of the eyelids as 

 if under the stimulus of a strong light. Movement of 

 the head to the opposite side is also frequently produced. 

 E.xtirpation of the angular gyrus on one side causes 

 complete blindness in the opposite eye, but this is not 

 permanent if the angular gyrus of the other hemisphere 

 be intact. If this also be removed the loss of vision is 

 complete and permanent. 



(3) The superior temporo-sphenoidal convolution is the 

 centre for hearing with the opposite ear. 



Evidence. — Electrical e.xcitation of this convolution 

 produces sudden retraction or pricking up of the opposite 

 ear, opening of the eyes, dilatation of the pupils, and 

 turning of the head and eyes to the opposite side. " These 

 phenomena resemble the sudden start and look of sur- 

 prise which are caused when a loud sound is made in the 

 opposite ear." Lesions of the temporo-sphenoidal lobe of 

 one side which involve the superior convolution produce 

 deafness of the opposite ear, as evidenced by the fact that 

 the animal becomes deaf to ordinary sounds when the ear 

 upon the same side as the lesion is stopped with cotton- 

 wool. When the lesion is established bilaterally, so as to 

 cause destruction of the superior temporo-sphenoidal con- 

 volution on both sides, the animal fails to respond to 

 auditory stimuli. 



(4) The hippocampal region is concerned with the 

 appreciation of tactile sensation, if not of other forms of 

 sensibility. 



Evidence. — Unilateral destruction of this region is fol- 

 lowed by complete absence of response to cutaneous 

 stimulation on the opposite side of the body (without any 

 true motor paralysis, although there may be disturbance of 

 voluntary movements, " due to the loss of tactile sensa- 

 tion, by which movements are guided ") " the effects being 

 of a persistent character." 



(5) Thesubiculum, or tip of the temporo-sphenoidallobe, 

 (under surface) is specially related to the sense of smell 

 (in the nostril of the same side). 



Evidence. — Electrical irritation of this part of the brain 

 causes phenomena (torsion of the lip and partial closure 

 of the nostril of the same side) such as are " produced by 

 the direct application to the nostril of a powerful or dis- 

 agreeable odour." Destruction of this region upon one 

 side is accompanied, when the nostril of the opposite side 

 is plugged, by impairment or loss of the olfactory sense : 

 bilateral destruction by complete absence of reaction to 

 olfactory sensations. " The comparative development of 

 this region in animals in which the sense of smell is 



