Bauhaus-Universität Weimar

Microscopical researches into the accordance in the structure and growth of animals and plants
Schwann, Theodor Schleyden
Nuclei, around which no cells have yet commenced to be de¬ 
veloped, may be observed in the cytoblastema between the 
cells in some situations ; for example, a and b. These like¬ 
wise contain a nucleolus, and are somewhat less than the nuclei 
in the smaller cells. 
The above observations furnish us with a complete repre¬ 
sentation of the development of cartilage-cells, and show the 
accordance of that process with the development of vegetable- 
cells, inasmuch as they exhibit the simultaneous presence in the 
cytoblastema both of simple nuclei, and of cells containing a 
nucleus of similar shape and size upon the inner surface of 
their walls, and which may be observed in all stages of tran¬ 
sition, from such as are scarcely larger than the nucleus they 
contain, to such as are many times its size. Simple nuclei are 
first present, developed in the cytoblastema. When these have 
arrived at a certain size, the cell is formed around and closely 
encompassing them. The cell gradually expands, whilst the 
nucleus remains lying on a point of the inner surface of its 
wall. The nucleus, also, increases somewhat in size, but not in 
proportion to the expansion of the cell. Now these three hy¬ 
potheses may be assumed from the above facts ; either the cell 
is first developed, and the nucleus subsequently, or both are 
developed simultaneously, or the nucleus is first developed, 
and then the cell around it. The first supposition, that the 
cells are developed earlier than the nuclei, is not possible, since 
in that case cells would be found at a certain period of deve¬ 
lopment without nuclei. The simultaneous development of a 
cell, together with its nucleus, as two distinguishable struc¬ 
tures, is equally impossible, for then we should observe a stage 
of development, at which as yet the cell and nucleus had not 
reached the size of the ordinary nucleus. In order to explain 
the above observations, we must, therefore, have recourse to 
the third supposition, viz. that the nucleus is first developed 
and then the cell around it. 
The form of the young cells depends upon the space allotted 
them for expansion. They are, therefore, either round or angular, 
according as the neighbouring cells permit of, or limit their re¬ 
gular expansion. Two or more cells are often developed close to¬ 
gether in one intercellular space, and thus compress those already 
formed, and the intercellular substance on the outside of them ;


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