Nucleus of the Animal and Vegetable " CelV 203 



From its property of originating the membrane of the cell, 

 Schleiden gave to the nucleus the name of Cytoblast or cell- 

 germ. In the cytoblast he saw what seemed a smaller body, 

 the nucleolus ; and he, as well as Schwann, Miiller, Valentin, 

 and Henle, supposed the smaller body to exist first, — the sub- 

 stance of the cytoblast, or larger body, they believed to be 

 deposited around the smaller one, — and the substance of the 

 membrane of the cell to be deposited around the cytoblast.* 



According to my observations, it is not so : I find the pro- 

 cess to be of a widely different character; so different, 

 indeed, that it may be termed the very opposite of that 

 supposed by the German physiologists just mentioned. It is 

 true that a minute pellucid, and, as will presently be seen, a 

 very important globule (fig. 1), exists before the ^-^^^ i, 

 cytoblast. But it is not true that a finely 

 gi'anular substance is " deposited around" that . 



pellucid globule, so as to make the nucleolus 0*0*^ 

 seen in the cytoblast identical with the previ- 

 ously existing pellucid globule. That previously existing 

 pellucid globule absorbs and assimilates new matter, and, at 

 the same time, enlarging and becoming finely granular, 

 assumes the form in fig. 4, the cytoblast of Schleiden, — hav- 

 ing prepared a nucleolus for itself. Nor is it true that the 

 membrane of the cell is formed around the cytoblast. The 

 outer part of the cytoblast rises in the form of membrane, so 

 as to produce fig. 5, a cell ; another portion of the cytoblast 

 enters into the formation of the contents of the cell ; and 

 what is left of the cytoblast in the cell-wall, becomes the 

 nucleus of the cell. 



This nucleus, said to remain inert in the cell-wall, or to 



* The following is the substance of a statement made by Valentin, as briefly 

 expressing the views on this subject of Schleiden, Schwann, Miiller, Henle, and 

 himself; and as being descriptive of the first formation of the elements of 

 tissues : — In a fluid, says he, there are precipitated granules, which are nu- 

 cleoli ; around the nucleolus there is deposited a finely granular substance, by 

 which there is formed the nucleus (cytoblast) ; and around the nucleus there is 

 formed the membrane of the cell. The principle of formation of the nucleus 

 around the nucleolus, is essentially the same as that of the cell around the 

 nucleus. Valentin concludes that this process may be described by the ex" 

 pression, heterogencoui caVcum-position. — Rei^crtoriura, 1839, ii., p. 284. 



