FEATHERS. 83 



time are surrounded by a dense capsule, which is composed, 

 throughout its entire thickness, of gigantic tabular epithelium. 

 The feather is so placed in this capsule, that the shaft and vane 

 arc folded together to form a hollow cylinder, which is occu- 

 pied by the so-called organized matrix of the feather (see an 

 article on this subject by Fr. Cuvicr, in Froriep's * Xotizen/ 

 No. 317). According to Cuvier, a membrane lines the inner 

 surface of the vane, and gives off septa, which penetrate be- 

 tween its separate barbs. This membrane, hoAvever, as well as 

 the septa, is composed of epithelium. 



The shaft of the feather consists of a loose medullary sub- 

 stance (the pith), surrounded by a firm cortex. On making 

 thin transverse or longitudinal sections of the pith, it is seen 

 to be composed of beautiful polyhedral cells, which perfectly 

 resemble the parenchymatous cellular tissue of plants, — as the 

 substance of cork for example. (See plate II, fig. 10.) The 

 cell-cavities which have moderately thick, dark partition-walls, 

 are at first filled with a transparent fluid, but subsequently 

 become dry, and in that state contain air. Notwithstanding, 

 however, that this pith so precisely resembles vegetable tissue 

 in its general appearance, it may be questioned whether these 

 cells be actually cells in that sense of the word in which we 

 receive it here, viz. elementary cells of organic structure, and 

 whether they correspond to vegetable cells. It therefore be- 

 comes necessary to investigate whether each cell has its pecu- 

 liar wall, and whether the course of development of each in- 

 dividual cell be the same as in plants. There is no structure, 

 however, in which it is easier to follow the process of develop- 

 ment than in the one before us, chiefly because the cells, 

 even from the first, have no connexion with the organized 



J o 



so-called matrix, but remain attached to the fully-developed 

 cells of the shaft, when the matrix, which terminates ex- 

 ternallv with a smooth surface, is taken away. The following 

 description is taken from the large wing-feather of a raven : 

 it applies however equally well to the feathers of the young 

 chicken. 



The pith, when in progress of formation, is soft and friable. 

 When a small portion of it is examined, after the component 

 particles have been separated asunder, it is found to consist 

 of cells, in various stages of development. Those which 



