THE CELL. 21 



The third place is taken by the so-called foam theory 

 (Butschli) ; a protoplasmic network forms a number of spaces 

 closed in on every side. All these spaces are filled with fluid. 

 In the angles of the foam-work fine granules (microsomes) are 

 contained. 



Finally there exists the granule theory (Altmann) according 

 to which the cells consist of fine granules which are distributed 

 in the jelly-like intergranular substance. These granules 

 Altmann claims to be the final elementary part of the cell, and 

 calls them, as the bearers of life, bioblasts. According to this 

 hypothesis, the granules play the principal role, and the inter- 

 granular substance only an accessory part. With regard to 

 the meaning of these two constituents of the cell, the first 

 three theories are quite opposed to the last. According to the 

 former, the granules of the protoplasm play a more subordi- 

 nate role. The intergranular substance of the granule theory is 

 identical with the essential protoplasm of the other three theories. 



In the protoplasm there are various substances not belong- 

 ing to it, which we include under the name protoplasmic or 

 cellular inclusions. To distinguish them from protoplasm, we 

 call them deutoplasm. Their nature is not constant. They 

 may be fat, carbohydrates, pigment granules, etc. 



These protoplasmic-inclusions (deutoplasm) occur in some 

 cases in such great quantity that the protoplasm itself becomes 

 inconspicuous and forms only a kind of network for the reserve 

 materials and secretion stored up there, as we may notice in 

 many egg cells and goblet cells. 



Fluid protoplasmic inclusions usually are present in spaces 

 called vacuoles. These spaces are made visible by dissolving- 

 out the contents. For example, fat droplets may be dissolved 

 in ether and the empty spaces left are plainly to be seen. 



The form which a mass of protoplasm or a whole cell takes 

 on may be various : spherical, cylindrical, flat, star-shaped, 

 spindle-shaped, or fibrillar. 



Cells vary in size from 3 u l to that of a bird's egg (e. g., an 

 ostrich egg, which is a simple cell). 



1 fj- = a micron = 0.001 mm. 



