v] Cffiiicd/ (tin? P(itlt<t](H/!cul Erlilciin 1 m/wW/m/ Function 137 



t\v<i). The ease recorded by Forster bears signs of thorough investigation and has been 

 t|uted frequently. The destruction was of course bilateral, approximately symmetrical and 

 chiefly c-i in fined to the mesial surt'aee of the occipital lobe. Microscopic examination of serial 

 sections showed that all the bands of fibres lying internal to and below the lateral ventricle, 

 including the inferior longitudinal bundle, were destroyed. A small portion of the apex of the 

 eiuieus and the cortex surrounding the hinder end of the calcarine fissure were left intact. 



In criticising this case von Monakow says that the most remarkable clinical feature 

 was, that in spite of the bilateral destruction of the mesially placed occipital convolutions, 

 central vision was retained ; and he makes full use of the case to substantiate a view which 

 he promulgates with some emphasis, viz., that there exists no part of the occipital cortex, 

 and possibly none of the cortex of the angular gyrus, with which the macula lutea is un- 

 connected. In other words, the macular field extends widely beyond the limits of the 

 generally accepted visual cortical area. But I cannot help thinking that von Monakow 

 is much too generous in regard to the reliance which he places on the case quoted, and 

 that more evidence is needed before we can consider this particular matter settled. And yet, 

 other observers who have worked at this subject do not enclose the visual area within our 

 narrow limits, although they include the calcarine cortex within their field. For instance kSeguin, 

 who analysed 40 cases, in all of which, be it noted, the lesion was in the region of the 

 fissura calcarina, roughly locates the visual centre on the inner surface of the occipital lobe. 

 Starr, from an examination of 27 cases, concludes that clinico-pathological material does not 

 allow of exact localisation, since a destructive lesion on either the inner or the outer surface 

 of the occipital lobe may occasion hemianopia. Vialet, who has contributed useful papers 

 on the cerebral centres of vision, containing accounts of eight cases all fully worked out, 

 assigns the following limits to the area, the parieto-occipital fissure in front, the margin of 

 the hemisphere above and behind, the inferior border of the third occipital convolution below ; 

 in other words, his field embraces the whole of the cuneus and the subjacent parts of 

 the lingual and fusiform lobules. 



Other writers extend the visual area on to the external occipital gyri, and even as far as 

 the angular gyms, after the doctrine of Ferrier ; and finally von Monakow, whose clinico-patho- 

 logical studies entitle him to first place amongst continental authorities on cerebral locali- 

 sation, and particularly on visual localisation, sums up the question in the following words' : 

 " Die Frage nach der wirklichen Ausdehnung der menschlichen Sehsphare lasst sich durch 

 klinische Beobachtungen mit nachfolgendem Sectionsbefund allein nicht losen, dies einerseits 

 wegen Circulationsverhaltnisse, anderseits wegen der Moglichkeit, neue Bahnen in dienst zu 

 stellen (Moment der Restitution). Aber gerade die Erfahrungen hinsichtlich des letzter- 

 wahnten Punktes, sowie hinsichtlich des Freibleibens der Macula selbst bei doppelseitigem 

 Ausfall beider Hinterhauptslappen in engeren Sinne, endlich die Resultate des Studiums 

 secundarer Veranderungen sprechen mit Nothvvendigkeit daftir, dass die Sehsphare ausser der 

 gesammten Rinde der eigeiitlichen Occipitahvindungen (Cuneus, Lobus lingualis, Gyrus de- 

 scendens, O.j O. ;i ) mindest.ens noch die hintere Partie des Gyr. angul. in sich schliesst." 



1 "Clinical observations with subsequent autopsies cannot alone decide the question of the real extent of the 

 human visual area, on account of peculiarities in its blood-supply on the one hand, and on account of the possi- 

 bility of new tracts being brought into operation on the other. But the evidence concerning the last-mentioned 

 point, along with that showing that the macula remains intact even after bilateral destruction of the occipital lobes 

 in the narrow sense, and finally the results of the study of secondary changes, necessarily suggest, that the visual area 

 occupies, in addition to the entire cortex of the individual occipital gyri (Cuneus, Lobus Lingualis, Gyrus Descendens, 

 Occ. 1 Occ. 3), at least the hinder part of the gyrus angularis." Gehirnpathologie, p. 468. 



C. IN 



