OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 337 



work in the nuclei. This is of course best shown in capillary 

 blood-vessels, on account of the thinness and transparency 

 of the wall. In some capillary vessels, when looking at the 

 wall from the surface, I have noticed from place to ])lace 

 fragments of a minute network ; it is quite possible that these 

 places correspond to the granular substance observed some- 

 times in the endothelial plates constituting the wall of the 

 capillary. Some such capillaries contained blood-corpuscles; 

 and the nuclei of these showed a very distinct network. I have 

 been able to recognise in some specimens apparently ccecal 

 dilatations of lymphatics, the nuclei of the endothelial wall 

 of which whether looked at from their broad or narrow side 

 presented the intranuclear 7ietwork with great distinctness, 

 and in all respects similar to that described of the other 

 nuclei. Also the nuclei of lymph-corpuscles jiresent in the 

 lymphatic exhibited a network of fibrils (see fig. 22). 



VI. The nerve-fibres. 



Without wishing to enter here into a description of the 

 distribution of nerve-fibres in the mesentery,^ I have only 

 to mention the extremely long, more or less wavy and curved 

 course the fine nerve-fibres pursue without giving off any 

 branches. Each such nerve represents a bundle of fine 

 fibrils, i.e. an axis cylinder, to which is applied from place 

 to place an oblong constricted or slightly folded nucleus. 

 The number of nuclei along such an axis cylinder depends on 

 the thickness of this latter. I measure, as far as this is pos- 

 sible in a fibre presenting a number of curvatures, three 

 successive segments from nucleus to nucleus, in fibre 

 (a): 0-1, 0-16, 0-128 mm.; in fibre {b): 0-16, 0-208, 

 0-14 mm. But in what appear to be the thinnest fibres 

 the length of a section between two nuclei reaches about 0-75 

 of a millemetre. 



The nuclei are oblong and slightly flattened ; their out- 

 line is not smooth, but is wavy or notched in, and therefore 

 looks as if folded. The mean size of such a nucleus is 

 0026 by 0006 or 0-008 mm. ; its outline, however, on 

 careful inspection is not very well defined, especially corre- 

 sponding to its poles we miss in many instances the limitinfT 

 membrane. Each nucleus is embedded in a hyaline plate 

 folded over the bundle of fibrils representing the nerve- 

 fibre; this plate — ground-plate we will call it — is very well 

 shown in specimens stained in hsematoxylin, or doubly 



^ I have described minutely the distribution of fine nerves in the 

 mesentery of frog in this Journal, Vol. XII, 1871; the niiniile nerves 

 belonging to the gronnd -substance of the mesentery appear to be far less 

 numerous in the newt ihau in the frojr. 



