6 INTRODUCTION 



Plastids, found chiefly in plant cells, aid in the formation of 

 starch and various pigments. Chlorophyll bodies, the centers of 

 formation of starch by photosynthesis, are considered the most 

 important of the chloroplastic type. 



Secretory granules of various chemical composition and physical 

 consistency, more or less transitory in nature, are found in secretory 

 cells. They dissolve to produce fat, mucin, or an enzyme. (See 

 page lo.) Storage granules are also quite generally distributed. 



Fibrillae, almost as characteristic as granules, appear in many 

 types of cells, including gland cells, nerve cells and muscle cells. 

 Fibrillae may be produced by the fusion of small granules, but like 

 certain other cytoplasmic inclusions, some fibrillae are regarded as 

 artifacts. 



The chondriosomes or mitochondria vary in form from granules 

 of 0.2 mu. to rods and filaments of much greater length. They are 

 found in most living cells and resemble albumins somewhat, both 

 in solubility and in staining reactions. The earlier technique of 

 fixation by acids such as acetic destroyed the mitochondria, but 

 they are shown successfully in living cells by Janus Green B. 

 Regaud suggested, as a possible explanation of their function, that 

 they are the centers of chemical action, and that they extract 

 substances from the protoplasm, transforming them into specific 

 intra-cellular structures. Cowdry has suggested that they supply 

 a surface-film, perhaps with a significance comparable to the nuclear 

 and cytoplasmic membranes.^ 



The Golgi apparatus is the term given to a group of cell-com- 

 ponents found widely distributed in both plant and animal cells. 

 They, like chondriosomes, require fixation by reagents lacking 

 acetic acid. Osmic acid fixers seem to show them best. The 

 apparatus appears in diffuse form as separate bodies, or in localized 

 form as a "Golgi net" consisting of concentrated fibrils. It has 

 been suggested by Nassanov, Bowen and others that the Golgi- 

 bodies have a secretory function. Bowen suggested that the Golgi 

 apparatus may be a center for the formation of enzymes. 



H. Hibbard (Arch. d'BioL, Tom. 38, p. i, 1927) and M. Parat 

 (Arch. d'Anat. mic, Tom. 24, p. 73, 1928) have shown that Golgi- 

 bodies may be depositions of the stain used. We are still in con- 

 siderable doubt regarding the function of Golgi-bodies, mitochon- 



' Consult Osterhout, W. J. V. 1929. Some aspects of permeability and bioelec- 

 trical phenomena. Bull. Nat. Res. Council, pp. 170-288, Washington, D. C. 



