14 NUCLEOLI. [SECT 8 



ish body, measuring on an average 0.002-0.004 of a line, rarely 

 attaining .oi -0.04 of a line, as in ganglionic globules and ova. 

 All nuclei are vesicles, as Schwann supposed, and as I recognised 

 as a general and original formation in embryos and adult animals 

 Their envelope is, in the smaller ones, very delicate, and appears 

 as a simple dark fine line; in the larger it is thicker, even of 

 measurable thickness, and bounded by double borders, as in the 

 nuclei of ganglionic globules, of ova, and of many embryos The 

 contents of the nuclear vesicles, apart from the nucleolus, almost 

 invariably consist of a clear or slightly yellowish, never dark, fluid 

 in which the same dark granules are perceptible by water and acetic 

 acid, as in the cells- on which account, even the nuclei never have 

 their natural homogeneous bright appearance in the usual methods 

 of investigation. More rarely, the nuclei contain formed con- 

 ten s, as the special granules in ova, termed germinal spots, as also 

 in the fat-cells of Pzsczcola (Leydig). With regard to the che- 

 mical character of nuclei, we have only this much to say, that 

 their membranes are nitrogenous, and in general do not differ ma- 

 terial y from the substance forming the younger cell-membranes; 

 sill they dissolve more slowly in alkalies, and are but little 

 attacked by diluted acetic and mineral acids: in, the latter charac- 

 ter this membrane approaches the elastic tissue, from which how 

 ever it is wry essentially distinguished, by its ready solubility in 

 alkalies Nuclei according to my observations, are found through- 

 out in all cells of embryos and adults as long as. the cells are still 

 young. Usually there is met with, in each cell, but one nucleus, 

 except when it multiplies : in this case, two or more nuclei appear 

 according to the number of cells about to be formed. In certain 

 cells, a greater number of nuclei are met with ; thus, in those of 

 the semen 4, 10, to 20, and more; as also in those of the epen- 

 dyma of the canalis medullas spinalis, in those of the supra-renal 

 capsules and of the hypophysis, in the hepatic cells of embryos, 

 those of the foetal marrow, and others. That nuclei also occur 

 free, and take part in the formation of certain tissues, has been 

 already mentioned. 



Nucleoli are round, sharply outlined, generally dark bodies 

 similar to fat-granules, measuring on an average o-qoio-oooic 

 of a line. Frequently they are almost immeasurably small; and 

 m embryos, m the germinal vesicles of ova, as germinal spots, and 

 in ganglionic globules attain to 0-003-001. Probably they are 

 everywhere vesicles, as may be inferred from their distinctly cir- 



