12 



INTRODUCTION PEOTOPLASM CELL 



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alveoli as hyaloplasm. The microsomes may in part be closely associated 

 with the alveolar walls, perhaps forming them and the spongioplasm by 

 the process of coalescence. The so-called alveolar 

 protoplasm is in reality of the granulo-alveolar type, 

 The spherules probably arise, at least in part, by a 

 process of liquefaction of some of the granules. The 

 alveologranular is probably the commonest type ot 

 protoplasm. The process of transformation of the 

 granular into the alveolar type can best be demon- 

 strated in young growing eggs of invertebrates. Fig. 

 13 shows an egg in which the perinuclear protoplasm 

 is predominantly alveolar, the more peripheral por- 

 tion granular. The metamorphosis is apparently 

 under the control of the nucleus. 



Other commonly described types of protoplasmic 

 structure may be interpreted in terms of mechanical 

 (extraneous; artificial) alterations in the alveolar type. Thus a rctimlur 

 type may be derived from the alveolar through modification (by pressure, 



FIG. 14. PANCREAS 

 CELL OF TURTLE, 

 FILLED WITH ZY- 

 MOGENIC GRAN- 

 ULES. 



n, nucleus, with 

 nucleolus. X 2000. 



FIG. 15. MOTOR NERVE CELL FROM THE VENTRAL HORN OF THE SPINAL CORD 



OF THE Ox. 



Showing Nissl granules in the cell body and its dendritic processes. The non- 

 granular process at the left is the axon. p, pigment. (From Barker's "The Nervous 

 System," after von Lenhossek.) 



