567:
time in his early career. Hering and
Helmholtz disagreed on almost everything and the controversy lasted long after the end of both of their lives. Hering however was by far the more aggressive of the two, and was always prompt to point out any mistake that Helmholtz might have made, sometimes even going so far as to insult him ("It is likely that the great Helmholtz in his dozing state..."). Helmholtz's faction (though probably not Helmholtz himself) spread rumors which accorded to Hering the need for help to do his mathematical work and that he was clinically insane ("He has been, as I have heard, mentally ill").
352:
429:
equal amounts, both eyes should move in the new binocular direction of the target (see Hering's law of visual direction above), then move in opposite direction to adjust vergence to that of the target. In other words, the eye in which the target did not move will move away and then back at the target. This prediction was experimentally confirmed by Yarbus in his seminal work on eye movements. However it is now known that strong deviations from Hering's law exist.
308:
516:
276:). There, he surprised the scientific community when he published, as a completely unknown scientist, his own mathematical derivation of the horopter independently from Hermann von Helmholtz, who was by then considered one of the best German scientists and mathematicians. Hering went as far as ridiculing Helmholtz's (unimportant) mathematical errors in his derivation of the horopter.
404:
44:
566:
Hering spent most of his life arguing violently with
Helmholtz. The controversy was not only scientific but also philosophical; Hering was a nativist, Helmholtz an empiricist. Helmholtz also came from a higher social class and was always considered a prodigy, whereas Hering had to go through a harder
428:
eye movements). Hering's law of equal innervation is best described by MĂĽller's stimulus where the fixation point changes position in 1 eye but not the other eye. Simplicity conducts that only the misaligned eye should move to refoveate. Hering's law predicts that because the eyes must always move by
289:
at the university of Prague where he remained for the next 25 years. There he became involved in fierce arguments between nationalistic Czechs who wanted the university taught in the language of the land, and a minority of German professors. Eventually a separate German university, Charles-Ferdinand
315:
Hering studied a broad range of subjects in vision, among them his outstanding studies on binocular vision. He derived, almost simultaneously with
Helmholtz, the theoretical shape of the horopter. Despite identical results, Hering's derivation was far more modern and elegant, using recently
245:
Hering was born in Alt-Gersdorf in Saxony, Germany. He probably grew up in a poor family, son of a
Lutheran pastor. Hering attended gymnasium in Zittau and entered the university of Leipzig in 1853. There he studied philosophy, zoology and medicine. He completed an M.D. degree in 1860.
491:. We now know that the human eye possesses three types of color-sensitive receptors (as proposed by Young, Maxwell, and Helmholtz) which then combine their signals in three color-opponent channels as proposed by Hering. Thus, both the Hering and Young-Helmholtz theories are correct.
460:. His evidence stemmed from color-adaptation experiments and the linguistic observation that certain color names cannot be combined into one. In this model, colors are perceived through mechanisms sensitive to three pairs of opponent colors: red-green, yellow-blue and white-black.
503:, or that artificially inflating the lungs triggers an automatic signal triggering expiration. Then deflating the lungs in turns triggers a new signal inducing respiration. That is, inspirations and expirations are an endless reflex loop triggering each other. He also showed the
824:"Alfred Volkmann (1863). Physiological Investigations in the Field of Optics (Physiologische Untersuchungen im Gebiete der Optik). Partial translation and Commentary; Supplement to Strasburger, H.; Huber, J.; Rose, D. (2018). "Ewald Hering (1899) On the Limits of Visual Acuity"
453:: red, green, and blue. Maxwell demonstrated that any color can be matched by a mixture of three primary colors. This was interpreted by Helmholtz as proof that humans perceive colors through three types of receptors, while white and black would reflect the amount of light.
284:
Hering was subsequently appointed professor of physiology at the military academy of Vienna until 1870. With better resources he conducted important studies in physiology, in particular on the cardiac and respiratory systems. In 1870, he succeeded
415:
to describe the conjugacy of eye movements in animals. According to this law eye movements are always equal in intensity in the two eyes but not in direction. Eye movements can therefore be either conjugate (in the same direction such as
316:
developed projective geometry. Indeed, Helmholtz himself qualified Hering's approach as "very elegant, comprehensive and complete". Subsequently, Hering empirically estimated the shape of the horopter. Alongside with
630:"Ernst Mach". Stanford Encyclopedia of Philosophy. 21 May 2008. Retrieved 4 September 2012. Hering and Mach were atheists, and disbelieved in a soul, but still accepted the idea that nature had internal direction.
163:
293:
In his late years, Hering returned to
Germany, where he became professor at the university of Leipzig in 1895, aged 61. He retired in 1915 and died of tuberculosis three years later. He was an atheist.
1337:
253:
was perhaps the most famous physiologist in
Germany. Hering seems to have applied for studying under his direction but was rejected, which might have contributed to his animosity towards
395:, the location information signalled by the involved receptors is coded to a much higher precision than would be possible by a single receptor, an explanation that still holds up today.
472:
that synthesizes both descriptions as one, where the Young-Helmholtz theory describes the interaction of light with receptors and Hering the image processing stage. Later, in 1925,
335:
which describes the perceived egocentric direction of an object from an observer. Unbeknownst to Hering and other visual scientists of the time, a similar law had been proposed by
733:"Ewald Hering (1899) On the Limits of Visual Acuity: A Translation and Commentary. With a Supplement on Alfred Volkmann (1863) Physiological Investigations in the Field of Optics"
671:
The theory of binocular vision: Ewald Hering (1868); edited by Bruce
Bridgeman and Lawrence Stark; translation and introduction by Bruce Bridgeman; commentary by Lawrence Stark
531:. When two straight and parallel lines are presented in front of radial background (similar to the spokes of a bicycle), the lines appear as if they were bowed outwards. The
655:
264:
After graduating, Hering practiced as a physician in
Leipzig. Despite having little time to do research and having even scarcer financial resources, he turned to
1332:
1327:
168:
261:. Although there is no evidence that Hering ever studied under their direction, in his later years he proudly acknowledged himself a "student of Fechner".
1317:
257:, Müller's protégé. However, in Leipzig, E. H. Weber and G. T. Fechner were conducting groundbreaking studies founding what would become the field of
551:
499:
Hering made significant contributions to the field of physiology as well as psychology. In particular he demonstrated with his student Breuer the
1261:
1126:
1073:
407:
Depiction of predictions for refoveating Muller's stimulus with eyes moving independently or eyes following Hering's law of equal innervation
379:
by about an order of magnitude. In his famous 1899 treatise "On the Limits of Visual Acuity" he summarized empirical data published 1863 by
391:
stimulus – a disalignment among two line segments – onto an idealized receptor array. He argued that, by a mechanism of integration across
412:
136:
332:
132:
1322:
678:
1197:
1103:
483:
Both theories have solid empirical evidence. The conundrum was resolved by the discovery of color-opponent ganglion cells in the
325:
128:
383:
and Ernst Anton WĂĽlfing 1892 who found that there are visual tasks in which spatial resolution goes well below the size of
229:
910:"In the year 1892, Wülfing showed that one can recognise differences in position that correspond to a visual angle of 12–10
1302:
712:
An Essay upon Single Vision with Two Eyes: Together with
Experiments and Observations on Several Other Subjects in Optics
1342:
488:
1312:
500:
124:
1307:
438:
286:
250:
324:, he noticed that the empirical horopter does not match the theoretical horopter, a phenomenon now named the
380:
148:
874:
Physiological
Investigations in the Field of Optics (Physiologische Untersuchungen im Gebiete der Optik)
446:
340:
254:
225:
210:
1004:
1297:
1292:
1019:
925:"Hering Hermeneutics: Supplement to Translation and Commentary of Hering (1899) by Strasburger et al"
473:
355:
Ewald Hering's model of how a Vernier acuity stimulus is coded by a receptor array. Receptors marked
504:
442:
1240:
1043:
649:
468:
463:
106:
588:
810:
1257:
1232:
1203:
1193:
1176:
1159:
1151:
1122:
1099:
1093:
1069:
1035:
954:
853:
780:
762:
674:
221:
68:
1224:
1027:
989:
985:
944:
936:
843:
835:
752:
744:
532:
524:
457:
265:
217:
116:
64:
17:
1190:
Organic memory: history and the body in the late nineteenth & early twentieth centuries
351:
973:
972:
Jiang, H.; Cottaris, N.; Golden, J.; Brainard, D.; Farrell, J. E.; Wandell, B. A. (2017).
528:
120:
608:
359:
signal a different position code along the horizontal direction from either the position
1023:
889:
949:
924:
848:
823:
757:
732:
543:
536:
421:
388:
152:
307:
1286:
710:
450:
376:
258:
1244:
1047:
392:
206:
202:
1277:
372:
144:
140:
515:
384:
321:
272:(the points in space that project on anatomically identical points on the two
186:
1155:
940:
839:
748:
1207:
1144:
Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
555:
403:
317:
1236:
1039:
958:
890:"Ueber den kleinsten Gesichtswinkel [On the smallest visual angle]"
857:
766:
590:
On the Limits of Visual Acuity. [Ueber die Grenzen der Sehschärfe]
507:
reflex, or that inflating the lungs triggers an acceleration of the heart.
43:
1180:
1163:
425:
417:
269:
1215:
Turner RS (1993). "Vision studies in Germany: Helmholtz versus Hering".
1031:
872:
480:. There he probes a formal relationship between the two color theories.
1254:
Visual Syntax, chapter from the book - Color, Facture, Art & Design
336:
86:
1119:
Origins of Neuroscience: A History of Explorations Into Brain Function
696:
Alhacen's theory of visual perception. Volume Two, English Translation
554:
and suggested that memories could be passed on through generations by
456:
Hering instead held that the visual system works based on a system of
387:
in the central retina. In an explanatory model, Hering superimposed a
249:
It is somewhat unclear how Hering trained to do research. At the time
547:
484:
273:
290:
University, was created in 1882 and Hering became its first rector.
209:, binocular perception, eye movements, and hyperacuity. He proposed
1228:
514:
402:
350:
306:
974:"Simulating retinal encoding: Factors influencing Vernier acuity"
437:
Hering disagreed with the leading theory developed primarily by
1066:
In the eye's mind: vision and the Helmholtz-Hering controversy
792:
Westheimer, Gerald (1975). "Visual acuity and hyperacuity".
478:
On the relation of the four color to the three color theory
546:
in an 1870 lecture for the Imperial Academy of Science in
375:: spatial resolution in certain visual tasks that exceeds
610:
On Memory and the Specific Energies of the Nervous System
1003:
Rucci, M.; Lovin, R.; Poletti, M.; Santini, F. (2007).
411:
Hering further studied eye movements. He developed the
449:. Young proposed that color vision is based on three
1059:
1057:
1005:"Miniature eye movements enhance fine spatial detail"
311:
Hering's demonstration of his law of visual direction
201:(5 August 1834 – 26 January 1918) was a German
731:
Strasburger, Hans; Huber, Jörg; Rose, David (2018).
182:
159:
112:
102:
94:
75:
50:
34:
726:
724:
722:
343:(1792) although both their laws were different.
268:(using both eyes together) and the problem of the
476:published a paper inspired by von Kries, titled
1256:. Hampshire, U.K.: Zero Books. pp. 65–82.
698:. Philadelphia: American Philosophical Society.
1338:Recipients of the Pour le MĂ©rite (civil class)
1068:. Princeton, N.J: Princeton University Press.
794:Investigative Ophthalmology and Visual Science
1175:. Clio Medica. Vol. 33. pp. 89–96.
1087:
1085:
8:
371:Hering did seminal work on what we now call
1278:Who Named It?, Karl Ewald Konstantin Hering
912:or even less" (translated from Hering 1899)
1173:Mach and Hering's physiology of the senses
654:: CS1 maint: location missing publisher (
42:
31:
1192:. Lincoln: University of Nebraska Press.
948:
847:
756:
550:. Hering took influence from the idea of
539:produces a similar, but inverted effect.
990:10.2352/ISSN.2470-1173.2017.14.HVEI-140
822:Strasburger, Hans; Rose, David (2018).
623:
597:Outlines of a Theory of the Light Sense
552:inheritance of acquired characteristics
647:
583:Spatial Sense and Movements of the Eye
7:
1333:Foreign members of the Royal Society
1328:Academic staff of Charles University
1121:. Oxford University Press. p. 338.
978:Human Vision and Electronic Imaging
542:Hering first suggested the idea of
230:German Charles-Ferdinand University
228:and became the first rector of the
1092:Moore, Walter John (29 May 1992),
535:is one of its variants, while the
331:Hering is also well known for his
25:
1318:People from the Kingdom of Saxony
413:Hering's law of equal innervation
137:Hering's law of equal innervation
877:. Leipzig: Breitkopf und Härtel.
562:The Hering-Helmholtz controversy
133:Hering's law of visual direction
642:Die Lehre vom binokularem Sehen
527:which now bears his name – the
1098:, Cambridge University Press,
577:The Theory of Binocular Vision
1:
1095:Schrödinger: Life and Thought
888:WĂĽlfing, Ernst Anton (1892).
523:In 1861, Hering described an
199:Karl Ewald Konstantin Hering
18:Karl Ewald Konstantin Hering
1142:Baumann C (June 1992). "".
923:Westheimer, Gerald (2018).
326:Hering–Hillebrand deviation
129:Hering–Hillebrand deviation
1359:
673:. New York: Plenum Press.
489:lateral geniculate nucleus
424:) or disjunctive (such as
1323:Leipzig University alumni
1117:Stanley, Finger. (1994).
871:Volkmann, Alfred (1863).
811:Link to Westheimer (1975)
205:who did much research in
192:
175:
141:Traube–Hering–Mayer waves
41:
941:10.1177/2041669518815921
894:Zeitschrift fĂĽr Biologie
840:10.1177/2041669518763675
749:10.1177/2041669518763675
603:Handbuch der Physiologie
287:Jan Evangelista Purkinje
224:, Hering studied at the
694:Smith, A. Mark (2001).
381:Alfred Wilhelm Volkmann
333:Law of Visual Direction
149:Opponent-process theory
1064:Turner, R. M. (1994).
935:(6): 204166951881592.
834:(3): 204166951876367.
743:(3): 204166951876367.
669:Hering, Ewald (1977).
640:Hering, Ewald (1868).
520:
466:published in 1905 the
408:
368:
312:
709:Wells, W. C. (1792).
518:
447:Hermann von Helmholtz
406:
363:code or the position
354:
310:
255:Hermann von Helmholtz
251:Johannes Peter MĂĽller
226:University of Leipzig
211:opponent color theory
1303:German physiologists
1252:Singh, Iona (2012).
1188:Otis, Laura (1994).
501:Hering–Breuer reflex
125:Hering–Breuer reflex
1032:10.1038/nature05866
1024:2007Natur.447..852R
519:The Hering illusion
443:James Clerk Maxwell
393:small eye movements
89:, Kingdom of Saxony
29:German physiologist
521:
464:Johannes von Kries
409:
369:
313:
107:Leipzig University
1343:Vision scientists
1263:978-1-78099-629-5
1127:978-0-262-01704-6
1075:978-0-691-03397-6
1018:(7146): 851–854.
715:. London: Cadell.
474:Erwin Schrödinger
222:Kingdom of Saxony
196:
195:
177:Scientific career
69:Kingdom of Saxony
16:(Redirected from
1350:
1313:Color scientists
1267:
1248:
1211:
1184:
1171:Janko J (1995).
1167:
1129:
1115:
1109:
1108:
1089:
1080:
1079:
1061:
1052:
1051:
1009:
1000:
994:
993:
969:
963:
962:
952:
920:
914:
908:
902:
901:
885:
879:
878:
868:
862:
861:
851:
819:
813:
808:
802:
801:
789:
783:
777:
771:
770:
760:
728:
717:
716:
706:
700:
699:
691:
685:
684:
666:
660:
659:
653:
645:
637:
631:
628:
533:Orbison illusion
525:optical illusion
303:Binocular vision
280:University posts
266:binocular vision
117:Canals of Hering
82:
61:
59:
46:
32:
21:
1358:
1357:
1353:
1352:
1351:
1349:
1348:
1347:
1308:German atheists
1283:
1282:
1274:
1264:
1251:
1214:
1200:
1187:
1170:
1141:
1138:
1136:Further reading
1133:
1132:
1116:
1112:
1106:
1091:
1090:
1083:
1076:
1063:
1062:
1055:
1007:
1002:
1001:
997:
984:(14): 177–181.
971:
970:
966:
922:
921:
917:
909:
905:
887:
886:
882:
870:
869:
865:
821:
820:
816:
809:
805:
791:
790:
786:
778:
774:
730:
729:
720:
708:
707:
703:
693:
692:
688:
681:
668:
667:
663:
646:
639:
638:
634:
629:
625:
620:
573:
564:
529:Hering illusion
513:
497:
458:color opponency
435:
401:
349:
305:
300:
282:
243:
238:
167:
151:
147:
143:
139:
135:
131:
127:
123:
121:Hering illusion
119:
103:Alma mater
90:
84:
80:
79:26 January 1918
71:
62:
57:
55:
37:
30:
23:
22:
15:
12:
11:
5:
1356:
1354:
1346:
1345:
1340:
1335:
1330:
1325:
1320:
1315:
1310:
1305:
1300:
1295:
1285:
1284:
1281:
1280:
1273:
1272:External links
1270:
1269:
1268:
1262:
1249:
1229:10.1086/368719
1212:
1198:
1185:
1168:
1137:
1134:
1131:
1130:
1110:
1104:
1081:
1074:
1053:
995:
964:
915:
903:
896:. Neue Folge.
880:
863:
814:
803:
784:
772:
718:
701:
686:
680:978-0306310164
679:
661:
632:
622:
621:
619:
616:
615:
614:
606:
600:
594:
586:
580:
572:
569:
563:
560:
544:organic memory
537:Wundt illusion
512:
511:Other research
509:
496:
493:
451:primary colors
434:
431:
422:smooth pursuit
400:
397:
389:Vernier acuity
385:receptor cells
348:
345:
304:
301:
299:
296:
281:
278:
242:
239:
237:
234:
194:
193:
190:
189:
184:
180:
179:
173:
172:
164:Pour le MĂ©rite
161:
157:
156:
153:Organic memory
114:
113:Known for
110:
109:
104:
100:
99:
96:
92:
91:
85:
83:(aged 83)
77:
73:
72:
63:
52:
48:
47:
39:
38:
35:
28:
24:
14:
13:
10:
9:
6:
4:
3:
2:
1355:
1344:
1341:
1339:
1336:
1334:
1331:
1329:
1326:
1324:
1321:
1319:
1316:
1314:
1311:
1309:
1306:
1304:
1301:
1299:
1296:
1294:
1291:
1290:
1288:
1279:
1276:
1275:
1271:
1265:
1259:
1255:
1250:
1246:
1242:
1238:
1234:
1230:
1226:
1223:(1): 80–103.
1222:
1218:
1213:
1209:
1205:
1201:
1199:0-8032-3561-5
1195:
1191:
1186:
1182:
1178:
1174:
1169:
1165:
1161:
1157:
1153:
1150:(3): 249–52.
1149:
1146:(in German).
1145:
1140:
1139:
1135:
1128:
1124:
1120:
1114:
1111:
1107:
1105:9780521437677
1101:
1097:
1096:
1088:
1086:
1082:
1077:
1071:
1067:
1060:
1058:
1054:
1049:
1045:
1041:
1037:
1033:
1029:
1025:
1021:
1017:
1013:
1006:
999:
996:
991:
987:
983:
979:
975:
968:
965:
960:
956:
951:
946:
942:
938:
934:
930:
926:
919:
916:
913:
907:
904:
899:
895:
891:
884:
881:
876:
875:
867:
864:
859:
855:
850:
845:
841:
837:
833:
829:
825:
818:
815:
812:
807:
804:
799:
795:
788:
785:
782:
781:G. Westheimer
776:
773:
768:
764:
759:
754:
750:
746:
742:
738:
734:
727:
725:
723:
719:
714:
713:
705:
702:
697:
690:
687:
682:
676:
672:
665:
662:
657:
651:
643:
636:
633:
627:
624:
617:
612:
611:
607:
604:
601:
598:
595:
593:
591:
587:
584:
581:
578:
575:
574:
570:
568:
561:
559:
557:
553:
549:
545:
540:
538:
534:
530:
526:
517:
510:
508:
506:
505:Traube-Hering
502:
494:
492:
490:
486:
481:
479:
475:
471:
470:
465:
461:
459:
454:
452:
448:
444:
440:
432:
430:
427:
423:
419:
414:
405:
399:Eye movements
398:
396:
394:
390:
386:
382:
378:
377:visual acuity
374:
366:
362:
358:
353:
346:
344:
342:
338:
334:
329:
327:
323:
319:
309:
302:
297:
295:
291:
288:
279:
277:
275:
271:
267:
262:
260:
259:psychophysics
256:
252:
247:
240:
235:
233:
231:
227:
223:
219:
214:
212:
208:
204:
200:
191:
188:
185:
181:
178:
174:
170:
165:
162:
158:
154:
150:
146:
142:
138:
134:
130:
126:
122:
118:
115:
111:
108:
105:
101:
97:
93:
88:
78:
74:
70:
66:
54:5 August 1834
53:
49:
45:
40:
33:
27:
19:
1253:
1220:
1216:
1189:
1172:
1147:
1143:
1118:
1113:
1094:
1065:
1015:
1011:
998:
981:
977:
967:
932:
929:i-Perception
928:
918:
911:
906:
897:
893:
883:
873:
866:
831:
828:i-Perception
827:
817:
806:
797:
793:
787:
775:
740:
737:i-Perception
736:
711:
704:
695:
689:
670:
664:
641:
635:
626:
609:
602:
596:
589:
582:
576:
571:Publications
565:
541:
522:
498:
482:
477:
467:
462:
455:
439:Thomas Young
436:
433:Color theory
410:
370:
364:
360:
356:
339:(1021) and
330:
314:
292:
283:
263:
248:
244:
218:Alt-Gersdorf
215:
207:color vision
203:physiologist
198:
197:
176:
81:(1918-01-26)
65:Alt-Gersdorf
36:Ewald Hering
26:
1298:1918 deaths
1293:1834 births
599:(1905/1964)
592:(1899/2018)
585:(1879/1942)
579:(1868/1977)
469:zone theory
373:hyperacuity
347:Hyperacuity
241:Early years
232:in Prague.
145:Hyperacuity
95:Nationality
1287:Categories
900:: 199–202.
800:: 570–572.
779:following
644:. Leipzig.
618:References
556:germ cells
495:Physiology
322:Hillebrand
187:Physiology
58:1834-08-05
1156:0941-293X
650:cite book
318:Helmholtz
236:Biography
213:in 1892.
1245:42940120
1237:11639585
1208:29638386
1040:17568745
959:30559959
858:29899967
767:29899967
426:vergence
418:saccades
298:Research
270:horopter
216:Born in
169:ForMemRS
1181:9061228
1164:1303712
1048:4416740
1020:Bibcode
950:6291878
849:5990881
758:5990881
337:Alhazen
274:retinas
87:Leipzig
56: (
1260:
1243:
1235:
1217:Osiris
1206:
1196:
1179:
1162:
1154:
1125:
1102:
1072:
1046:
1038:
1012:Nature
957:
947:
856:
846:
765:
755:
677:
613:(1897)
605:(1879)
548:Vienna
485:retina
183:Fields
171:(1902)
166:(1911)
160:Awards
98:German
1241:S2CID
1044:S2CID
1008:(PDF)
367:code.
341:Wells
1258:ISBN
1233:PMID
1204:OCLC
1194:ISBN
1177:PMID
1160:PMID
1152:ISSN
1123:ISBN
1100:ISBN
1070:ISBN
1036:PMID
982:2017
955:PMID
854:PMID
763:PMID
675:ISBN
656:link
487:and
445:and
320:and
76:Died
51:Born
1225:doi
1028:doi
1016:447
986:doi
945:PMC
937:doi
844:PMC
836:doi
753:PMC
745:doi
420:or
1289::
1239:.
1231:.
1219:.
1202:.
1158:.
1148:89
1084:^
1056:^
1042:.
1034:.
1026:.
1014:.
1010:.
980:.
976:.
953:.
943:.
931:.
927:.
898:11
892:.
852:.
842:.
830:.
826:.
798:14
796:.
761:.
751:.
739:.
735:.
721:^
652:}}
648:{{
558:.
441:,
328:.
220:,
67:,
1266:.
1247:.
1227::
1221:8
1210:.
1183:.
1166:.
1078:.
1050:.
1030::
1022::
992:.
988::
961:.
939::
933:9
860:.
838::
832:9
769:.
747::
741:9
683:.
658:)
365:b
361:a
357:c
155:+
60:)
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
