8 PROTOPLASMIC THEORY OF LIFE. 



matter can die into or rearrange itself in a short time 

 into a number of different forms, which shall possess 

 exactly the same physical properties in the vital as in 

 the ordinary state of combination. It is likewise to 

 be expected that as the vital or metabolic molecular 

 changes in the living matter must be very rapid and 

 complicated, the physical state of it cannot be hard or 

 rigid, and this agrees with what has been long known of 

 the parts in which life is most active and intense, viz., 

 the gra} T matter of the nervous system. Moreover, 

 we know that there is no example of life existing in 

 any gaseous or purely liquid fluid. These considera- 

 tions narrow the probable field of the seat of vitality 

 very much, and the following question thereupon 

 is raised by Fletcher : " Admitting that irritability or 

 vitality, general and specific, is a property of the 

 organized solids alone, it becomes a question of the 

 highest interest whether it be directly inherent in 

 each of the organized tissues, either of plants or 

 animals, or whether it merely appears to be possessed 

 by them all in virtue of -some one which is universally 

 distributed over the organized being, and inextricably 

 interwoven with every other " (ii. p. 55). He ex- 

 amines this question, and by an interesting train of 

 reasoning, based chiefly on arguments derived from 

 comparative anatomy and physiology, he comes to 

 the conclusion that vitality is not inherent in any 

 liquid, nor in any of the rigid structures, and 

 that it is only in virtue of a specially living matter, 

 universally diffused and intimately interwoven with 

 its texture, that any tissue or part possesses vitality. 

 Therefore, he " must deny any direct participation in 



