THE CELL DOCTRINE. 81 



consist of almost pure germinal matter (Plate, Fig. 

 1), imbedded in a soft, mucus-like, yet continuous 

 formed matter. These masses of germinal matter 

 divide and subdivide, pushing the older masses to- 

 wards the surface, to make up for those which are 

 constantly exfoliated. While this is going on, how- 

 ever, the germinal matter keeps increasing in size 

 until the cells arrive half way towards the surface, by 

 absorption of nutrient pabulum, which has to work 

 its way through any formed material already exist- 

 ing. At the same time, a portion of the germinal 

 matter is being converted into formed material, 

 which accumulates on its surface, within that already 

 formed, stretching it, and becoming more or less in- 

 corporated with it. Thus, both constituents of the cell 

 increase up to a certain point, the cells constantly growing 

 in consequence. As new cells are, however, produced 

 from below, the older ones are removed farther and 

 farther away, the formed matter becoming more and 

 more impervious to nutrient pabulum. At length a 

 point is attained when the entire cell ceases to in- 

 crease in size, since no pabulum reaches the masses 

 of germinal matter, though the latter is still being 

 converted into formed material. Hence, the masses 

 of germinal matter actually grow smaller, as the cell 

 increases in age; and when the periphery is reached, 

 there remains but a small nucleus of germinal matter, 

 with a large quantity of formed material. Thus, we 

 are enabled to judge of the age of the cell by the 

 relative quantity of germinal matter and formed ma- 

 terial ; if the former be large, and the latter small, 

 the cell is young, whereas, if the opposite relation 



