5 8 AGE, GROWTH, AND DEATH 



accumulated (Fig. 16, A). When this raw material is 

 turned over into secretion by a chemical change, it is 

 discharged from the cell, the cell loses in volume, and in 

 its shrunken state presents a very different appearance, 

 as is shown at B in the figure. It is necessary for the 



FIG. 16. Two SECTIONS OF THE PANCREATIC GLAND OF A DOG. A, the 

 cells are enlarged by the accumulation of material to form the secretion. B< 

 the cells are shrunk because there has been prolonged secretion and part of 

 their substance is lost. From R. Heidenhain. 



cells to again elaborate the material for secretion be- 

 fore they can a second time become functionally active. 

 Here we have something of the secret of the produc- 

 tion of the various juices in the body revealed to us. 

 Other excellent examples of the differentiated con- 

 dition of the cells are afforded us by the examination 



