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The Course and Distribution of the Arteries Supplying the Visual (Striate) Cortex*
AMERICAN JOURNAL OF OPHTHALMOLOGY VOLUME
61
JUNE, 1966
NUMBER
6
T H E COURSE AND DISTRIBUTION O F T H E ARTERIES SUPPLYING T H E VISUAL ( S T R I A T E ) CORTEX* CARLTON G.
S M I T H , M.D.,
AND WINIFRED F.
G. RICHARDSON,
M.D.
Toronto, Canada T h e origin of the arteries supplying the visual sensory area of the cerebral hemi sphere and the manner in which the branch es of each one are distributed within this area were studied to provide data that might be useful in the interpretation of visual field defects resulting from occlusion of one of these vessels. MATERIAL AND M E T H O D
T h e arteries of the medial surface of the occipital lobe and the adjacent parts of the parietal and temporal lobes were studied in one of the hemispheres, right or left, of each of 32 normal brains as they became avail able at autopsy. T h e arteries were cleaned, using a dissector's loupe to preserve the finest branches demonstrable with this magnification. A drawing was then made of the medial aspect of the hemisphere to record the course and branches of these vessels. I n order to record the course and distribution of the vessels within the calcarine and parie to-occipital sulci, these sulci were drawn with the walls separated as in F i g u r e 1-A. After charting the arteries, the outline of the visual area was obtained by slicing the occipital lobe and noting the extent of the cortex in which the line of Gennari could be seen. OBSERVATIONS
The visual area. T h e visual area is some what elliptical with a rounded posterior bor der and a pointed anterior end (fig. 1 ) . Its
long axis is along the floor of the calcarine sulcus and its upper and lower halves lie in its upper and lower walls, respectively. T h e posterior part of the visual area is wider than the anterior part and extends five to 10 m m behind, above and below the sulcus. T h e width of this marginal part of the visu al area varies from specimen to specimen, with the depth of the calcarine sulcus and with the presence and height of gyri that may cross its floor. I n Figure 1-A, one of these gyri crosses the floor and rises to the medial surface of the hemisphere, dividing the calcarine sulcus into anterior and poste rior portions. A t the junction of the calcarine and par ieto-occipital sulci, the borders of the visual area recede from the medial surface and disappear in the calcarine sulcus. Within the sulcus, on its upper and lower walls, each of the borders follows the crest of a gyrus that extends toward the floor with a slight incli nation anteriorly (fig. 1-A). Therefore, the visual area tapers to a point located on the floor of the sulcus just in front of its junc tion with the floor of the parieto-occipital sulcus. T h e anterior end of the visual area is one cm. in front of the lower end of the unopened parieto-occipital sulcus. The vessels of the visual area. T h e whole visual area is supplied by the calcarine ar tery in some individuals, but usually there are supplementary branches from one or more other arteries, namely, the posterior temporal and the parieto-occipital branches of the posterior cerebral, and the occipital branches of the middle cerebral. T h e visual area illustrated in Figure 1 has supplemen-
♦From the Department of Anatomy, Univer sity of Toronto. 1391
F L o o r of P a r l e t o occipi,Î.aL S u t c u » "Upper B o r d e r of Visual· A r e a Gyrus a c r o s s Catcar-ί,ηβ SuL-ous Mtddte CerebralA r t e r y JtBPV
P a r t e * oocotpttctL Artery -
Post·. Temp. A
Fig. 1 (Smith and Richardson). (A) The medial surface of the occipital portion of a left hemi sphere to illustrate features of the visual area (outlined by a broken line), and its vessels (see text). The walls of the calcarine and parieto-occipital sulci are separated and a small segment of a gyrus is removed at the lower border of the visual area to show the line of Gennari. (B) A diagram of the visual area of (A), showing the vascular subdivisions outlined by broken lines. (C) The right half of the visual field of each eye, showing the portion of the field projecting to each vascular subdivision of the visual area.
ARTERIES SUPPLYING THE VISUAL CORTEX tary branches from all the vessels that may contribute to this area. In this study of 32 hemispheres, the visu al area was supplied by the calcarine artery only in eight; by the calcarine and the pos terior temporal arteries in 11 ; by the calca rine and parieto-occipital arteries in six; by the calcarine and both the parieto-occipital and posterior temporal in five; by the calca rine plus the middle cerebral and the parietooccipital in one ; and by all the above arteries in one. The contribution of the posterior tempo ral artery to the visual area. This artery helped to supply the visual area in 17 of the 32 specimens. It arose from the posterior cerebral two cm or less below the calcarine sulcus and coursed backward below it to ward the occipital pole. When the contribu tion of this vessel to the visual area was minimal, it sent terminal branches to the posterior inferior part, that is, the macular region. As it increased its contribution to the supply of the visual area its terminal branches extended into the upper macular area and collateral branches invaded succes sively more anterior portions from below. The largest contribution of this vessel to the supply of the visual area in our series was to the posterior half of the upper por tion and all of the inferior half. Occlusion of this vessel in some cases could result in a quadrantic form of hemianopia. The contribution of the parieto-occipital artery to the visual area. This artery had branches supplying the visual area in 12 of 32 specimens. In most cases these branches were short and supplied only a small part of the anterior superior border of the visual area, as illustrated in Figures 1-B and 2-C. However, as pointed out by Beauvieux and Ristich-Goelmino,1 a long branch may come off the distal part of the parieto-occipital ar tery and arch back to end in the posterior superior part of the macular area. This less common branch was present in three of our 32 specimens. The contribution of the middle cerebral to the visual area. Branches to the visual area
1393
from the middle cerebral artery were en countered in two of the 32 specimens. The branches were terminal twigs that turned around the occipital pole from the lateral surface and extended for five to 10 mm into the superior part of the portion of the area receiving the macular projection. The calcarine artery. The calcarine artery is described in textbooks of anatomy as a terminal branch of the posterior cerebral that follows the calcarine sulcus from end to end and has a distribution limited to the visual area. In our series the artery followed the calcarine sulcus in only eight of the 32 specimens and in no case were its branches limited to the visual area. The course and branching of the calcarine artery varies a great deal, but for descrip tive purposes the calcarine arteries of the 32 specimens may be grouped as follows: In five specimens (fig. 2-A) the artery was located on the floor of the calcarine sul cus and its branches extended onto the upper and lower walls and beyond the sul cus to supply the marginal part of the visual area and portions of the cortex adjacent to the visual area. In three specimens the artery followed the calcarine sulcus at the medial surface of the hemisphere (fig. 2-B). In these cases the vessel gave off a series of collateral branch es to the floor of the sulcus where each of them extended a short distance posteriorly. Other collateral branches extended up and down to supply the marginal parts of the visual area located on the medial surface. In 11 specimens, the calcarine artery came off the posterior cerebral a little below the calcarine sulcus (fig. 2-C) and crossed the visual area obliquely upward and back ward. In three of the 32 specimens the calcarine artery came off the posterior cerebral a little above the calcarine sulcus and supplied only the upper part of the visual area. The lower part was supplied by the posterior temporal artery. This pattern is not included in Fig ure 2. In the 10 remaining specimens, the calca-
V i s u a l , F i e l d Of Each Eye Right Left half half
ΑΛ/SuaV Area Of Lreft Hemvsphere
A Calcarine Art on floor of Calcarine Suloua
£> Coloorvne Art. f o l l o w s Cale. S. on m e d . s u r f a c e of h e m i s p h e r e
Branch t o ■f l o o r of· » u l c u s Parietooccipital Artery
/ C a l c a r i n e Art. crosses visual area o b l i q u e l y
Ώ. Calc. Art. has a lonq br. on f l o o r of Calc. S u l c u s
C a l c . Art. h a s an upper a n d a .Lower longitudinal branch
Calc. Art.
Fig. 2 (Smith and Richardson). Diagrams illustrating variations in the course and branching of the calcarine artery. The heavy line in the diagram of the visual field to the right of each example outlines the portion of the field that projects to the patch of cortex supplied by the vessel marked by a small circle close to its origin.
ARTERIES SUPPLYING THE VISUAL CORTEX rine artery branched as it approached the visual area to form two longitudinal vessels. In four of these, one of the two vessels coursed along the anterior part of the floor of the calcarine sulcus (fig. 1 and fig. 2-D) and supplied a portion or all of a longitudi nal band of cortex that receives the projec tion from the sector of the visual field ex tending horizontally from the center of fixa tion. In six other specimens in which the cal carine artery divided into two longitudinal trunks, the two vessels were well separated and were so disposed that the upper one supplied the upper part of the visual cortex and the lower one the remainder (fig. 2-E). In two of these specimens the vessels ap peared to share equally in the supply of the visual area; therefore, occlusion of either one of the vessels in these specimens could have produced a quadrantic hemianopia. The portions of the visual field repre sented in the vascular subdivisions of the visual area. Although the general features of the projection of the retina, and thus of the visual field, onto the visual cortex have been documented in man (Holmes 2 ), the precise projection of each of the concentric bands of the retina, or visual field, is not known; hence, certain assumptions have to be made in attempting to relate small subdi visions of the cortex to portions of the visual field. In the diagrams of Figures 1 and 2, the visual field is, for convenience, divided into four concentric bands. These, in turn, are assumed to project to the four portions of the visual area marked off by lines drawn at right angles to its long axis. The posterior and largest portion of the visual area thus demarcated is the one that is considered to receive the projection from the central part of the visual field. The three anterior por tions of the visual area are assumed to re ceive, in order, the projections from the three successively more peripheral concen tric bands of the visual field. Using these diagrams of the visual area
1395
and visual field, the portion of the field represented within the area of distribution of each of the vessels was charted as in Fig ure 1-C. These charted subdivisions of the visual field are similar in shape and location to the visual field defects that are encoun tered in patients when vessels of the visual area are occluded (Hughes, 3 Harrington 4 ). In Figure 2 additional examples are given, illustrating the form and location of portions of the visual field believed to be represented in vascular subdivisions of the visual area. COMMENT
A survey of the representative patterns of vessels supplying the visual (striate) cortex (fig. 1 and 2) reveals that the calcarine ar tery usually supplies most of the visual area but, in three fourths of the specimens, it was not the only vessel supplying this area nor was its distribution restricted to this area. Therefore, in man the calcarine artery is not set apart for the supply of a function al unit of cortex, that is, the visual sensory area, as suggested by Shellshear5 and Abbie.6 Branches of the posterior temporal artery helped to supply the visual area in about half of the specimens examined. This is significant because these branches always supply a part of the "macular" area of cor tex and could therefore be a factor in the preservation of central vision when the cal carine artery is occluded. Beauvieux and Ristich-Goelmino1 drew attention to the presence and the possible significance of this vessel in macular spar ing and also described the branch from the parieto-occipital artery that may extend into this part of the visual field. Our results in dicate that, in addition to these two vessels which may extend into the posterior part of the visual area, there may be a direct con tribution from the middle cerebral artery. An attempt has been made to correlate portions of the visual area of cortex sup plied by a small artery with portions of the
1396
CARLTON G. SMITH AND WINIFRED F. G. RICHARDSON
visual field. T h e findings indicate that these derived portions of the visual field, like the visual field defects resulting from occlusion of a cortical vessel, may be sectorlike bands extending radially from the center of fixa tion, or arclike bands concentric with the center of fixation, or a combination of these, as illustrated by the lower branch of the calcarine artery shown in Figure 1. O u r observations also reveal that it is possible for the upper half of the visual area to be supplied by one longitudinal ves sel and the lower half by another. These may be two branches of the calcarine or be branches of the calcarine and the posterior temporal arteries, respectively. SUMMARY
T h e origin and course of the arteries of the cortex of the visual area were traced with a dissector's loupe in one hemisphere of 32 human brains and the distribution of each branch was charted in a drawing of that specimen. A n attempt was then made to relate the area of distribution of each
branch supplying the visual cortex to the portion of the retina represented in that area. F o u r arteries, the calcarine, the posterior temporal, the parieto-occipital and the mid dle cerebral may contribute to the supply of the visual area. T h e variations in the con tribution of each and the basic patterns formed by the branches of the calcarine ar tery are described. REFERENCES
1. Beauvieux and Ristich-Goelmino : De la vascularisation du centre cortical de la mucula. Arch. ophthal. 43 :S, 1926. 2. Holmes, G. and Lister, W. T.: Disturbances of vision from cerebral lesions, with special refer ence to the cortical representation of the macula. Brain, 39:34, 1916. 3. Hughes, E. B. : The Visual Fields. Springfield, 111., Thomas, 19S4. 4. Harrington, D. O. : Textbook and Atlas of Clinical Perimetry. St. Louis, Mosby, 1964, ed. 2. 5. Shellshear, J. L. : A contribution to our knowledge of the arterial supply of the cerebral cortex in man. Brain, 50:236, 1927. 6. Abbie, A. A. : The blood supply of the visu al pathways. M. J. Australia, 11:199, 1938.
E X P E R I M E N T A L U V E I T I S : II* G.
SELZER, F .
C.
P A T H . , AND M A U R I C E H .
LUNTZ,
F.R.C.S.
Johannesburg, South Africa AND M.
I.
S A C K S , M.
MED.
PATH.
Jerusalem, Israel I n the first part of this study, 1 the evi dence for hypersensitivity as an etiologic factor in anterior uveitis was discussed, and experimental procedures for producing uveitis in guinea pigs using heterologous uveal protein as an antigen were described. A mild uveitis occurred following extraocu-
lar sensitization without ocular trauma, but the best results were obtained when the uvea was injected intraocularly or subconjunctivally in sensitized guinea pigs. Some of these animals developed sympathetic ophthalmia in the opposite, nontraumatized eye.
* From the C.S.I.R. and University of Cape Town Virus Research Unit and the Department of Ophthalmology, Medical School, University of Witwatersrand.
I n a parallel series of experiments, lens protein instead of uveal protein was used as antigen. I n another experiment, antisera prepared in guinea pigs to bovine lens and
61
JUNE, 1966
NUMBER
6
T H E COURSE AND DISTRIBUTION O F T H E ARTERIES SUPPLYING T H E VISUAL ( S T R I A T E ) CORTEX* CARLTON G.
S M I T H , M.D.,
AND WINIFRED F.
G. RICHARDSON,
M.D.
Toronto, Canada T h e origin of the arteries supplying the visual sensory area of the cerebral hemi sphere and the manner in which the branch es of each one are distributed within this area were studied to provide data that might be useful in the interpretation of visual field defects resulting from occlusion of one of these vessels. MATERIAL AND M E T H O D
T h e arteries of the medial surface of the occipital lobe and the adjacent parts of the parietal and temporal lobes were studied in one of the hemispheres, right or left, of each of 32 normal brains as they became avail able at autopsy. T h e arteries were cleaned, using a dissector's loupe to preserve the finest branches demonstrable with this magnification. A drawing was then made of the medial aspect of the hemisphere to record the course and branches of these vessels. I n order to record the course and distribution of the vessels within the calcarine and parie to-occipital sulci, these sulci were drawn with the walls separated as in F i g u r e 1-A. After charting the arteries, the outline of the visual area was obtained by slicing the occipital lobe and noting the extent of the cortex in which the line of Gennari could be seen. OBSERVATIONS
The visual area. T h e visual area is some what elliptical with a rounded posterior bor der and a pointed anterior end (fig. 1 ) . Its
long axis is along the floor of the calcarine sulcus and its upper and lower halves lie in its upper and lower walls, respectively. T h e posterior part of the visual area is wider than the anterior part and extends five to 10 m m behind, above and below the sulcus. T h e width of this marginal part of the visu al area varies from specimen to specimen, with the depth of the calcarine sulcus and with the presence and height of gyri that may cross its floor. I n Figure 1-A, one of these gyri crosses the floor and rises to the medial surface of the hemisphere, dividing the calcarine sulcus into anterior and poste rior portions. A t the junction of the calcarine and par ieto-occipital sulci, the borders of the visual area recede from the medial surface and disappear in the calcarine sulcus. Within the sulcus, on its upper and lower walls, each of the borders follows the crest of a gyrus that extends toward the floor with a slight incli nation anteriorly (fig. 1-A). Therefore, the visual area tapers to a point located on the floor of the sulcus just in front of its junc tion with the floor of the parieto-occipital sulcus. T h e anterior end of the visual area is one cm. in front of the lower end of the unopened parieto-occipital sulcus. The vessels of the visual area. T h e whole visual area is supplied by the calcarine ar tery in some individuals, but usually there are supplementary branches from one or more other arteries, namely, the posterior temporal and the parieto-occipital branches of the posterior cerebral, and the occipital branches of the middle cerebral. T h e visual area illustrated in Figure 1 has supplemen-
♦From the Department of Anatomy, Univer sity of Toronto. 1391
F L o o r of P a r l e t o occipi,Î.aL S u t c u » "Upper B o r d e r of Visual· A r e a Gyrus a c r o s s Catcar-ί,ηβ SuL-ous Mtddte CerebralA r t e r y JtBPV
P a r t e * oocotpttctL Artery -
Post·. Temp. A
Fig. 1 (Smith and Richardson). (A) The medial surface of the occipital portion of a left hemi sphere to illustrate features of the visual area (outlined by a broken line), and its vessels (see text). The walls of the calcarine and parieto-occipital sulci are separated and a small segment of a gyrus is removed at the lower border of the visual area to show the line of Gennari. (B) A diagram of the visual area of (A), showing the vascular subdivisions outlined by broken lines. (C) The right half of the visual field of each eye, showing the portion of the field projecting to each vascular subdivision of the visual area.
ARTERIES SUPPLYING THE VISUAL CORTEX tary branches from all the vessels that may contribute to this area. In this study of 32 hemispheres, the visu al area was supplied by the calcarine artery only in eight; by the calcarine and the pos terior temporal arteries in 11 ; by the calca rine and parieto-occipital arteries in six; by the calcarine and both the parieto-occipital and posterior temporal in five; by the calca rine plus the middle cerebral and the parietooccipital in one ; and by all the above arteries in one. The contribution of the posterior tempo ral artery to the visual area. This artery helped to supply the visual area in 17 of the 32 specimens. It arose from the posterior cerebral two cm or less below the calcarine sulcus and coursed backward below it to ward the occipital pole. When the contribu tion of this vessel to the visual area was minimal, it sent terminal branches to the posterior inferior part, that is, the macular region. As it increased its contribution to the supply of the visual area its terminal branches extended into the upper macular area and collateral branches invaded succes sively more anterior portions from below. The largest contribution of this vessel to the supply of the visual area in our series was to the posterior half of the upper por tion and all of the inferior half. Occlusion of this vessel in some cases could result in a quadrantic form of hemianopia. The contribution of the parieto-occipital artery to the visual area. This artery had branches supplying the visual area in 12 of 32 specimens. In most cases these branches were short and supplied only a small part of the anterior superior border of the visual area, as illustrated in Figures 1-B and 2-C. However, as pointed out by Beauvieux and Ristich-Goelmino,1 a long branch may come off the distal part of the parieto-occipital ar tery and arch back to end in the posterior superior part of the macular area. This less common branch was present in three of our 32 specimens. The contribution of the middle cerebral to the visual area. Branches to the visual area
1393
from the middle cerebral artery were en countered in two of the 32 specimens. The branches were terminal twigs that turned around the occipital pole from the lateral surface and extended for five to 10 mm into the superior part of the portion of the area receiving the macular projection. The calcarine artery. The calcarine artery is described in textbooks of anatomy as a terminal branch of the posterior cerebral that follows the calcarine sulcus from end to end and has a distribution limited to the visual area. In our series the artery followed the calcarine sulcus in only eight of the 32 specimens and in no case were its branches limited to the visual area. The course and branching of the calcarine artery varies a great deal, but for descrip tive purposes the calcarine arteries of the 32 specimens may be grouped as follows: In five specimens (fig. 2-A) the artery was located on the floor of the calcarine sul cus and its branches extended onto the upper and lower walls and beyond the sul cus to supply the marginal part of the visual area and portions of the cortex adjacent to the visual area. In three specimens the artery followed the calcarine sulcus at the medial surface of the hemisphere (fig. 2-B). In these cases the vessel gave off a series of collateral branch es to the floor of the sulcus where each of them extended a short distance posteriorly. Other collateral branches extended up and down to supply the marginal parts of the visual area located on the medial surface. In 11 specimens, the calcarine artery came off the posterior cerebral a little below the calcarine sulcus (fig. 2-C) and crossed the visual area obliquely upward and back ward. In three of the 32 specimens the calcarine artery came off the posterior cerebral a little above the calcarine sulcus and supplied only the upper part of the visual area. The lower part was supplied by the posterior temporal artery. This pattern is not included in Fig ure 2. In the 10 remaining specimens, the calca-
V i s u a l , F i e l d Of Each Eye Right Left half half
ΑΛ/SuaV Area Of Lreft Hemvsphere
A Calcarine Art on floor of Calcarine Suloua
£> Coloorvne Art. f o l l o w s Cale. S. on m e d . s u r f a c e of h e m i s p h e r e
Branch t o ■f l o o r of· » u l c u s Parietooccipital Artery
/ C a l c a r i n e Art. crosses visual area o b l i q u e l y
Ώ. Calc. Art. has a lonq br. on f l o o r of Calc. S u l c u s
C a l c . Art. h a s an upper a n d a .Lower longitudinal branch
Calc. Art.
Fig. 2 (Smith and Richardson). Diagrams illustrating variations in the course and branching of the calcarine artery. The heavy line in the diagram of the visual field to the right of each example outlines the portion of the field that projects to the patch of cortex supplied by the vessel marked by a small circle close to its origin.
ARTERIES SUPPLYING THE VISUAL CORTEX rine artery branched as it approached the visual area to form two longitudinal vessels. In four of these, one of the two vessels coursed along the anterior part of the floor of the calcarine sulcus (fig. 1 and fig. 2-D) and supplied a portion or all of a longitudi nal band of cortex that receives the projec tion from the sector of the visual field ex tending horizontally from the center of fixa tion. In six other specimens in which the cal carine artery divided into two longitudinal trunks, the two vessels were well separated and were so disposed that the upper one supplied the upper part of the visual cortex and the lower one the remainder (fig. 2-E). In two of these specimens the vessels ap peared to share equally in the supply of the visual area; therefore, occlusion of either one of the vessels in these specimens could have produced a quadrantic hemianopia. The portions of the visual field repre sented in the vascular subdivisions of the visual area. Although the general features of the projection of the retina, and thus of the visual field, onto the visual cortex have been documented in man (Holmes 2 ), the precise projection of each of the concentric bands of the retina, or visual field, is not known; hence, certain assumptions have to be made in attempting to relate small subdi visions of the cortex to portions of the visual field. In the diagrams of Figures 1 and 2, the visual field is, for convenience, divided into four concentric bands. These, in turn, are assumed to project to the four portions of the visual area marked off by lines drawn at right angles to its long axis. The posterior and largest portion of the visual area thus demarcated is the one that is considered to receive the projection from the central part of the visual field. The three anterior por tions of the visual area are assumed to re ceive, in order, the projections from the three successively more peripheral concen tric bands of the visual field. Using these diagrams of the visual area
1395
and visual field, the portion of the field represented within the area of distribution of each of the vessels was charted as in Fig ure 1-C. These charted subdivisions of the visual field are similar in shape and location to the visual field defects that are encoun tered in patients when vessels of the visual area are occluded (Hughes, 3 Harrington 4 ). In Figure 2 additional examples are given, illustrating the form and location of portions of the visual field believed to be represented in vascular subdivisions of the visual area. COMMENT
A survey of the representative patterns of vessels supplying the visual (striate) cortex (fig. 1 and 2) reveals that the calcarine ar tery usually supplies most of the visual area but, in three fourths of the specimens, it was not the only vessel supplying this area nor was its distribution restricted to this area. Therefore, in man the calcarine artery is not set apart for the supply of a function al unit of cortex, that is, the visual sensory area, as suggested by Shellshear5 and Abbie.6 Branches of the posterior temporal artery helped to supply the visual area in about half of the specimens examined. This is significant because these branches always supply a part of the "macular" area of cor tex and could therefore be a factor in the preservation of central vision when the cal carine artery is occluded. Beauvieux and Ristich-Goelmino1 drew attention to the presence and the possible significance of this vessel in macular spar ing and also described the branch from the parieto-occipital artery that may extend into this part of the visual field. Our results in dicate that, in addition to these two vessels which may extend into the posterior part of the visual area, there may be a direct con tribution from the middle cerebral artery. An attempt has been made to correlate portions of the visual area of cortex sup plied by a small artery with portions of the
1396
CARLTON G. SMITH AND WINIFRED F. G. RICHARDSON
visual field. T h e findings indicate that these derived portions of the visual field, like the visual field defects resulting from occlusion of a cortical vessel, may be sectorlike bands extending radially from the center of fixa tion, or arclike bands concentric with the center of fixation, or a combination of these, as illustrated by the lower branch of the calcarine artery shown in Figure 1. O u r observations also reveal that it is possible for the upper half of the visual area to be supplied by one longitudinal ves sel and the lower half by another. These may be two branches of the calcarine or be branches of the calcarine and the posterior temporal arteries, respectively. SUMMARY
T h e origin and course of the arteries of the cortex of the visual area were traced with a dissector's loupe in one hemisphere of 32 human brains and the distribution of each branch was charted in a drawing of that specimen. A n attempt was then made to relate the area of distribution of each
branch supplying the visual cortex to the portion of the retina represented in that area. F o u r arteries, the calcarine, the posterior temporal, the parieto-occipital and the mid dle cerebral may contribute to the supply of the visual area. T h e variations in the con tribution of each and the basic patterns formed by the branches of the calcarine ar tery are described. REFERENCES
1. Beauvieux and Ristich-Goelmino : De la vascularisation du centre cortical de la mucula. Arch. ophthal. 43 :S, 1926. 2. Holmes, G. and Lister, W. T.: Disturbances of vision from cerebral lesions, with special refer ence to the cortical representation of the macula. Brain, 39:34, 1916. 3. Hughes, E. B. : The Visual Fields. Springfield, 111., Thomas, 19S4. 4. Harrington, D. O. : Textbook and Atlas of Clinical Perimetry. St. Louis, Mosby, 1964, ed. 2. 5. Shellshear, J. L. : A contribution to our knowledge of the arterial supply of the cerebral cortex in man. Brain, 50:236, 1927. 6. Abbie, A. A. : The blood supply of the visu al pathways. M. J. Australia, 11:199, 1938.
E X P E R I M E N T A L U V E I T I S : II* G.
SELZER, F .
C.
P A T H . , AND M A U R I C E H .
LUNTZ,
F.R.C.S.
Johannesburg, South Africa AND M.
I.
S A C K S , M.
MED.
PATH.
Jerusalem, Israel I n the first part of this study, 1 the evi dence for hypersensitivity as an etiologic factor in anterior uveitis was discussed, and experimental procedures for producing uveitis in guinea pigs using heterologous uveal protein as an antigen were described. A mild uveitis occurred following extraocu-
lar sensitization without ocular trauma, but the best results were obtained when the uvea was injected intraocularly or subconjunctivally in sensitized guinea pigs. Some of these animals developed sympathetic ophthalmia in the opposite, nontraumatized eye.
* From the C.S.I.R. and University of Cape Town Virus Research Unit and the Department of Ophthalmology, Medical School, University of Witwatersrand.
I n a parallel series of experiments, lens protein instead of uveal protein was used as antigen. I n another experiment, antisera prepared in guinea pigs to bovine lens and