A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . n thissystem of vessels and the cerebral—except through thebasilar trunk—is by small branches of the precere-bellars and postcerebrals across the crura cerebri. 347 Brain, Circulation In REFERENCE HANDBOOK OF THE MEDICAL SCIENCES CiKCLE OF Willis.—The carotid ends at the outerangle of the chiasma in two main branches, the pre-and medicerebral arteries. At about one centimeterin front of the chiasm the two precerebrals are con-nected by the precommunicant. From eith
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . n thissystem of vessels and the cerebral—except through thebasilar trunk—is by small branches of the precere-bellars and postcerebrals across the crura cerebri. 347 Brain, Circulation In REFERENCE HANDBOOK OF THE MEDICAL SCIENCES CiKCLE OF Willis.—The carotid ends at the outerangle of the chiasma in two main branches, the pre-and medicerebral arteries. At about one centimeterin front of the chiasm the two precerebrals are con-nected by the precommunicant. From either themedicerebral or the carotid passes the postcommuni-cant to the corresponding post cerebral. Hence the cir-cle (or polygon) of Willis Ls made up by one precommu-nicant, two precerebrals, two medicerebrals (or twocarotids), two postcommunicants, and two postcere-brals. This is the classical arrangement; from it,however, there are frequent and important found that it held in only 70, or, overlookingany disproportion in the postcommunicants, in 119out of 200 cases. Only in the apes do the vertebrals. 10Fig. 1003.—Arteries of the Base. (After Duret ) 1, Carotid; 2, medicerebral; 3, pre-cerebral; 4. postcerebral; 5, preperforants (striate arteries): 6, prechoroid; 7, postcom-municants; S, postchoroid; 9, medichoroid; 10, callosals (termination of precerebrals): 11,medioptics; 12, prethalamie (postperforants). The carotids are drawn frontad to showthe preperforants. The left temporal lobe is cut away, exposing tlio medicerebral trunkat the bottom of the Sylvian fissure, and also its branches crossing the insula. nearly equal the carotids. In man, Ehrmann, from 157 measurements, found that very constantly the basilartrunk was equal to one carotid ( furnished one-third of the brain supply). The communicants arenot simply to reestablish a circulation in case ofobliteration, but they normally act to equalize pres-sure in the local vessels. When this cir
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
