412 



OF SLOW AND RAPID GROWTH. 



alcohol. It may permeate the tissues and produce 

 changes in them. Many other active agents are 

 taken up by the blood, and under certain circum- 

 stances produce a direct action upon the tissues. 

 These substances may then undergo change, and 

 perhaps be completely decomposed, and their elements 

 excreted in an altogether different state of combina- 

 tion from the body. Being transmitted by the blood 

 to different parts of the body such soluble materials 

 may modify the growth of tissues and affect the rate 

 at which growth takes place. Nay, we know that 

 by certain soluble matters introduced from without 

 circulating with the blood the formation and growth 

 of tissues may be actually prevented. For the further 

 elucidation of the matter under consideration, it is 

 desirable to refer briefly to the varying rate of growth 

 of bioplasm under altered conditions of life. 



Of slow and rapid growth. We can tell at once, 

 by the characters of a cell, whether it has been grow- 

 ing quickly or slowly. Whenever the outer part of the 

 cell (formed material) is firm and hard, and not very 

 permeable to nutrient matter, the growth must have 

 been slow. Where on the other hand, the envelope is 

 very thin, or where there is no envelope or cell-wall at 

 all, the greatest facilities for rapid growth exist. Con- 

 trast the pus-corpuscle, consisting almost entirely of 

 bioplasm, which has grown perhaps in the course of 

 a few hours, with a fully formed cuticular cell, in 

 which the bioplasm is surrounded by a very thick 



