EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 83 



at the under surface of the nail. The horny tissue of the hoofs of 

 animals, also consists in the foetus entirely of cells. 



4. Feathers. The medullary substance of feathers is composed of 

 polyhedral cells. In the young feather, a nucleus is visible in the wall 

 of each of these cells. The cells are developed around small nuclei, 

 which lie in great number in a finely granular matter. This formation 

 of new cells takes place, not in old parent cells, but near the surface of 

 the vascular matrix of the feather, which affords the cytoblastema. 

 Some of the nuclei contain nucleoli. The fibres of the cortical part of 

 the shaft of the feather are produced from large band-like epithelium 

 cells, which contain nuclei and nucleoli. These cells become resolved 

 into several fibres, while all trace of the cell disappears. The barbs 

 of the feathers are themselves miniature feathers ; the secondary shafts 

 have the same structure as the main shaft, while the secondary barbs 

 or barbules in their turn consist at first of nucleated cells applied to 

 each other by their edges. 



5. The Crystalline lens. The fibres of the crystalline lens are developed 

 from the cells first observed by Werneck. In the lens of a chick after 

 eight days' incubation there are as yet no fibres, but merely pale round 

 cells, some of which contain a nucleus. In lenses further developed, 

 some of the larger cells contain one or two smaller cells in their inte- 

 rior. In embryo pigs, measuring three and a half inches in length, 

 the greater part of the fibres of the lens is already perfect ; but a part 

 is still not completely formed ; and there are besides many round 

 cells which are about to undergo their metamorphosis. The perfect 

 fibres compose a nucleus in the centre of the lens. The next fibres 

 are seen to be tabular prolongations of globular cells. The dentated 

 orders of these cells, like those of some vegetable cells, are formed sub- 

 sequently, 



(To be continued.) 



<;tract0 antf &b3tractg from dfamgn Staurnal*. 



[From Valentin's Repertorium, 1841.] 



Decaisne on the Structural development of the Generative System of 

 Viscum album. The male flowers may be detected almost a year before 

 anthesis. At first the anthers are only distinguishable from the adjacent 

 green periantheal expansions by their want of colour, they being other- 

 wise composed of the same kind of cells. At a later period numerous 

 spaces, filled with a mucous fluid, are seen, from which mucus other 

 cells, larger than the adjacent ones, and kept together by a transparent 



G 2 



