160 University of California Publications in Anatomy L'^oi" 2 



halves of the maculae (upper homonymous quadrants of the macular 

 portion of the visual fields). The fovea centralis in particular is pro- 

 jected upon a middle zone stretching across the pole and, in the 

 monkey, across the operculum of the occipital lobe fairly horizontally. 

 In the monkey the foveal projection is probably close to the shallow, 

 impression, the external calcarine sulcus or superior occipital sulcus, 

 dividing- the operculum occipitale into an upper and a lower half. 



(e) The horizontal meridian, dividing the upper homonymous 

 extramacular quadrants of both hemiretinae and of the crossed monoc- 

 ular portion and corresponding portions of the visual fields from 

 lower quadrants, extends in a longitudinal sense, along the bottom of 

 the fissura calcarina. Its continuation around the occipital pole and, 

 in the monkey, over the occipital operculum approximately toward the 

 midpoint of the sulcus simialis, corresponds with the horizontal merid- 

 ian dividing the upper and lower quadrants of both homonymous 

 hemimaculae. The vertical line dividing both homonymous halves of 

 the visual fields of both eyes and passing through the points of fixation 

 is represented by the posterior boundary of the striate area; in the 

 monkey it stretches in a fairly parallel way along the sulcus simialis. 

 The points of fixation must, therefore, correspond with a central 

 point of that boundary. The dividing line between the macular and 

 extramacular cortex probably has the shape of a sickle with both its 

 horns inclined occipitalward embracing the macular portion of the 

 striate area in front along both ascending and descending branches 

 of the fissura calcarina (in the monkey). Since both horns of the 

 extramacular cortex terminate in sharply extended wedges, the macu- 

 lar cortex in its posterior, and in the monkey in its opercular portion, 

 is not completely surrounded by the extramacular cortex. 



(9) The bilateral or the double cortical representation of each total 

 macula, with each and all of its receptor elements connected with both 

 hemispheres, has no anatomical foundation. The individual macular 

 elements are represented only in one hemisphere. But each half of 

 each macula is projected upon another hemisphere. In other words, 

 each macular cortex represents homonymous halves of both maculae. 



(10) The entire striate area, receives everywhere afferent visual 

 fibers. There exist no visible gaps (small cortical zones without an 

 afferent fiber supply) which might separate small supplied cortical 

 islets. The number of afferent visual fibers per cortical square unit 

 appears to be larger in the occipital pole and in the occipital operculum 

 than in the calcarine fissure (in the monkey). The coarse exogenous 



