The Cell 



91 



(g) Centrosome, a small spherical body often found in the cyto- 

 plasm of animal cells near the nucleus. It is looked upon as the dynamic 

 center in cell division. 



If the student is to study Medicine he will probably find an advan- 

 tage in dividing the various definitely discernible substances in the 

 cytoplasm, into Mitochondria, Plasmosomes, and Paraplasmic sub- 

 stances. 



Mitochondria 1 (Fig. 27). These are little granules, rods, and threads 

 in the protoplasm, quite constant in the various cell bodies, at least, of 

 the animal world. In fact, one investigator insists that it is these 

 mitochondria, rather than the chromosomes, which are the bearers of 

 heredity; while another insists that they accumulate at both poles of the 

 cell, and are converted into secretory granules. 



Plasmosomes. 2 These are tiny granules distinguished from the 

 mitochondria because they are concerned with the housekeeping of the 

 cell, that is, with the assimilation of food materials, with forming various 

 secretions, and with the excretion of waste matter. Plasmosomes have 

 not been seen, but are supposed to be present because certain substances 

 are produced in the cells which must be due to something physical or 



Fig. 27. Mitochondria as they appear in the Sex Cells of Dividing Sperm of Blaps. 



a. Scattered granular mitochondria. 



b. Rod-shaped. 



c. Rods drawn out around spindle. (After Duesberg.) 



chemical. This is shown by the fact that the products of the cell form 

 little swellings of various kinds. These swellings take a stain, and 

 it is the particles which cause these swellings, or cell-products, which 

 are known as plasmosomes. The cell-products consist largely of fat 

 and carbohydrates, and may be stored in the cells. Cell products are 

 called cytofacts or metaplasm. (This latter term is applied because such 

 substance is due to metabolism.) 



Golgi apparatus (Fig. 28). Very recently by a special staining 

 method known as Golgi's silver impregnation method, it has been found 



1 While some medical men usually speak of mitochondria, and some of the older writers use 

 the term bioplasts, plastidules, archoplasmic granules, plastosomes, plastochondria, chondrioconts, 

 plastoconts and chondriomites, depending on the shape of the mitochondria, the name cytologists 

 use is that of Chondrio somes, so that the student must think of mitochondria and chondriosomes as 

 interchangeable terms. 



2 Medical men are inclined to use the term plasmosomes as here given, but cytologists use the 

 term only to mean true nucleoli. These latter workers never use it in the sense we have given it 

 in this book. 



