“I 
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PUS-CORPUSCLES. 
The low grade of development held by the class of cells now 
under consideration, in which those elementary formations re- 
tain their greatest degree of individuality, is indicated by the 
fact that it presents so very few modifications. The mucus-, 
pus-, and lymph-corpuscles are small round cells with a nucleus 
attached to their walls. According to Henle, mucus- and 
pus-corpuscles cannot be distinguished in any way from one 
another, and those of lymph differ from them only imasmuch 
as their nucleus is more round and granulous, and does not 
crumble under the action of acetic acid. No difference exists 
between them in the form of the entire cell. The blood-cor- 
puscles present a higher degree of development in this class. 
In them we not only find very characteristic cell-contents, 
the red colourimg matter, but the form of the cell also under- 
goes an important alteration, inasmuch as it becomes flattened. 
As this flattening takes place in cells which float free in a 
fluid, it cannot be explained as the result of mechanical causes, 
but must manifestly be regarded as a peculiar stage of deve- 
lopment of these cells. The nucleus is persistent in all these 
cells, whilst in those more highly developed it usually disappears 
at some subsequent period. Throughout this class the cyto- 
blastema is a fluid; and it is present in greater quantity than 
we shall find to be the case in the next class. If the egg be 
included in this class, we have yet another peculiarity in the 
cells to be added to the above; viz. that not only have the 
separate yelk-cells cell-contents consisting of distinct granules, 
but that the development of the yelk-cells within the yelk 
considered as one cell, is a formation of cells within cells, and 
in some of these cells even a second enclosure takes place. 
This peculiarity, however, is one which may almost be said to 
stand in inverse ratio to the importance of the tissue. It 
is most frequent, perhaps indeed universal, in vegetables, 
occurs more rarely in animals, as in the egg, crystalline lens, 
cartilage, and so on, and appears to be altogether absent in 
the higher structures, as areolar tissue, muscle, &c. We 
have already discussed the other peculiarities of the cells of the 
egg. In the following class we shall not only find a greater 
change in the form of the cells. from flattening, but we shall 
also become acquainted with many other different modifica- 
tions of them. 
