Literary Notices. xxi 



axial bundle end freely in the tectum. The marginal optic bundle 

 arises from axis cylinders from cells of one of the deep layers. In 

 these respects the results agree with Herrick's in the fish, reptile and 

 amphibia, but we do not think the layers are capable of such close 

 discrimination as that attempted by Wlassak. 



The author did not succeed in applying the method of degenera- 

 tion to the tectum and does not make the very desirable comparisons 

 with the Urodela and other groups. The paper, nevertheless is very 

 serviceable, especially as it is introductory to physiological work. 



We hope similar care may be used in seeking the cerebral con- 

 nections. 



Histology of the Optic Nerve and Tract. 1 



Professor S. E. Hensen finds the path of the optic stimuli to be 

 composed of fibres from the large ganglion cells of the retina which end 

 in the geniculate bodies, and other fibres arising in cells of the genicu- 

 lata and ending in the cortex of the occipital lobe. The course and posi- 

 tion of the fibre bundles is as follows : The macular bundle, which 

 at the papilla lies latero-ventrally, becomes more central as it passes 

 centrad, and is the central bundle in the chiasm and tract. The un- 

 crossed fibres at the papilla form two bundles, a dorso-lateral, and a 

 ventro-lateral, separated by the macular fibres ; further back these 

 unite to form a lateral bundle. The crossed fibres at the papilla lie 

 in a medial or dorso-medial plane and retain this position throughout 

 their course. On entering the chiasm, the uncrossed fibres, which 

 have hitherto formed a compact crescentic bundle, divide into a num- 

 ber of horizontal rays which alternate with similar rays formed by the 

 crossed fibres. A certain proportion of the uncrossed fibres keeps its 

 course at the periphery of the chiasm, but most of them pass medially, 

 intermingling with the crossed fibres. The crossed fibres in passing 

 through the chiasm, change from the dorso-median position to 

 a ventro-median position in the tract. The uncrossed fibres 

 also change, occupying in the tract a latero-dorsal position. 

 Fibres representing the dorsal half of the retina run dorsad 

 in both bundles. These bundles remain separate as far as 

 to the geniculatum where they coalesce. The optic fibres, in 

 part, form the capsule of the geniculate body and, in part, enter it, 

 forming the so-called medullary lamella?. The geniculate body is, 

 therefore, the main visual ganglion, though fibres can be traced to the 



'Om Synbanans anatomi ur diagnostik synpunkt. Upsala, 1893. 



