. Il fundus oculi di uccelli, specialmente visto dall'oftalmoscopio; uno studio sull'anatomia comparativa e fisiologia. Sepiments anastomose l'uno con l'altro. Questo è il tipo ben noto tra i mammiferi. Uccelli mostrano una peculiarità; all'aspetto interno del nervo le partizioni del piale penetono-trate perpendicolarmente nella sostanza del nervo e non anastomose fino a che theyreach circa metà nello spessore del cordone. Analoghe parti perpendicolari, ma molto brevi, esistono a volte sul lato esterno. Il risultato è che il nerveha un aspetto fogliato, specialmente markedon i
1198 x 2085 px | 20,3 x 35,3 cm | 8 x 13,9 inches | 150dpi
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. The fundus oculi of birds, especially as viewed by the ophthalmoscope; a study in the comparative anatomy and physiology . sepiments anastomose with each other.This is the type well known among Mammals.Birds exhibit one peculiarity; at the inner aspect of the nerve the pial partitions pene-trate perpendicularly into the substance ofthe nerve and do not anastomose until theyreach about half way into the thickness ofthe cord. Analogous perpendicular parti-tions, but very short, exist sometimes on theexternal side. The result is that the nervehas a foliated appearance, especially markedon the internal side. The Pecten, Marsupium, Fan or Combof Birds By means of the ophthalmoscope and directillumination there is seen, below and exter-nally, in the fundus of every bird, a blackmass of variable form. When the free edgeof this organ is illuminated one notices alongitudinal strip with undulating edges.If one throws the light upon the base of thisobject — the pecten or comb — the papillalooks like a sparkling white area whose mar-gins are edged with black, the center beingoccupied by the irregular, black mass.. Fig. 13 Diagram Showing the Relations of the Optic NerveEntrance to the Pecten and the Basilar Artery andVein in the Sparrow. (Wood and Slonaker.) A, artery to pecten, which sends a branch along each fold;ch, choroid; on, optic nerve; pect, pecten; ret, retina;scl, sclerotic; v, vein from pecten, which receives abranch from each angle of the folds. ANATOMY OF THE FUNDUS ORGANS IN BIRDS 23 The pectinate image seems to be displacedby abrupt movements in the vitreous mass, disturbances due probably to contractions ofthe ocular muscles, external and internal. As Kalt says, the pecten is a membranousorgan covered by a black pigment attached tothe optic nerve and projecting a variabledistance into the vitreous body. This organ, studied and described for the first time byPerrault, in 1876, received later the namecomb (peigne). The term comb is notexact since there are no
