LIFELESS MATTER WITHIN CELLS. 



17 



have a branching, irregular form, and are separated by solid 

 calcareous matter which is unmistakably lifeless. These ex- 

 amples show that the lifeless matters of the body often occur in 

 the form of deposits between living cells by which they have 

 been produced. In all such cases the embryonic tissue consists 

 at first of living cells in direct contact, or separated by only a 

 very small quantity of lifeless matter. In later stages the 

 cells may manufacture additional lifeless substance which 

 appears in the form of firm partition- walls between the cells, 

 or as a matrix, solid or liquid, in which the cells lie. When 

 solid walls are present they are often perforated by narrow chan- 

 nels through which the protoplasmic cell-bodies remain in con- 

 nection. (See Figs. 4, 8, and 50.) 



Lifeless Matter within Living Cells. Equally important with 

 the deposit of lifeless matter between cells is the formation of life- 

 less matter within cells, either (a) by the deposition of various sub- 

 stances in the protoplasm, or (b) by the direct transformation of 

 the whole mass of protoplasm. Examples of the first kind are 



i.c 



P 



FIG. 9. A group of cells from the stem of a geranium 

 (Pelargonium), showing lifeless substances (starch 

 and crystals) within the protoplasm. As in Fig. 2, 

 each cell contains a large central vacuole, filled 

 with sap ; c, groups of crystals of calcium oxalate ; 

 i.e., intercellular space ; n, nucleus ; s, granules of 

 starch, (x 300.) 



FIG. 10. (After Ranvier.) - 

 Group of "adipose cells" 

 from the tissue beneath the 

 skin (" subcutaneous con- 

 nective tissue 1 ') of an em- 

 bryo calf, t showing drops of 

 fat in the protoplasm. /, fat- 

 drops (black) ; , nuclei 

 (X 550.) 



mineral crystals (Fig. 9), grains of starch (Fig. 9), drops of 

 water, and many other substances found within, the cells of 

 plants. Among animals drops of fat (Fig. 10) and calcareous 



