OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 829 



oval nuclei at more or less regular intervals. The nuclei 

 measure in the mean O'OIS by 0"014 mm., and show in all 

 instances an exquisitely pretty network uniformly pervading 

 their interior. This intranuclear network possesses the same 

 characters as that described of the cells of the stomach. The 

 network varies in form and arrangement between that of a 

 delicate net and that of a honeycomb of a sponge ; the bright 

 dots to be observed in it correspond mostly to fibrils seen in 

 optical section. There are no structures comparable to 

 the nucleolus. In some parts of the specimen we find 

 the endothelial membrane of the surface broken up into 

 isolated plates corrcS[)onding to the individual endothelial 

 cells, or into smaller groups — two or three — of them. 

 The isolated endothelial cells show generally a single 

 excentric nucleus — in exceptional instances the nucleus is 

 double — and are in many instances more or less folded or rolled 

 up. If we get the endothelial plates in our specimen clear of 

 the membrane of the mesentery and unfolded we notice that 

 their substance shows a beautiful network of fibrils, such as I 

 attempted but only imperfectly succeeded to delineate iu 

 figs. 1.3, 14, and 15 ; in the drawings the network is com- 

 posed of far too coarse fibrils. The fibrils are exceedingly 

 delicate, run in bundles which anastomose and thus form a 

 fenestration with large or smaller fenestrse. At first sight, 

 and looked at with only a moderately high power they 

 (fibrils) seem to be only streaks of a ' granular substance.' 

 That this latter is composed of fibrils becomes clear when 

 examined more carefully and with a higher power, such as 

 Zeiss F, or Hartnack luim, 10. Thus we have to distinguish 

 also in the endothelial plates a hyaline ground-substauce, 

 which I wish to call ground-plate, and in it a network of 

 fibrils — the intracellular netivork. Thus network is in all 

 endothelial cells of our specimens in direct communication 

 with the intranuclear network (see figs. 13, 14, and 15.) In 

 groups of endothelial plates not showing the outlines of the 

 individual cell-plates we notice that the intracellular fibrils 

 of one plate merge into those of its neighbours, apparently 

 without any distinct interruption. 



Schwalbe^ describes each of the endothelial cells lining 

 the canal of Schlemm as consisting of a hyaline, delicate 

 plate, with an oval nucleus and 'reticular thickenings;' in 

 figs. 30 and 31 accompanying his paper this arrangement 

 is well shown on isolated endothelial plates prepared in 

 Miiller's fluid. I have no doubt that these 'reticular thick- 



' " Uuters. liber d. Lyniphbalmen d. Auges," &c., ' Arcbiv. f. Mikr. 

 Auatom,,' Bd. vi, p. 305. 



