212 "PROTOPLASM" OF MUSCLE. 



for a little fluid is expressed from the substance of 

 the contractile material during contraction, and taken 

 up again as it returns to the previous quiescent con- 

 dition. The constant repetition of similar changes is 

 characteristic of contractile tissues. 



The states of rest, of partial contraction, and com- 

 plete contraction, are but different degrees of the self- 

 same process of shortening of a delicate fibre. This 

 contractile fibre perhaps consists of a passive basic 

 substance of a fibrous character, through which is 

 diffused a soft material prone to move in directions 

 at right angles to one another, according to the 

 manner in which external forces operate upon it. 

 The changing substance upon which the alteration 

 depends can be expressed from the muscular tissue, 

 and coagulates spontaneously like the fibrin of blood. 

 Young muscles yield a larger proportion of this 

 material than old ones, but I do not think that it is 

 derived solely from the bioplasm of muscle. 



257. " Protoplasm " of Muscle. The contractile 

 tissue of muscle has been considered to be a form of 

 "protoplasm," and muscular contraction has been 

 attributed to the " contractile property," supposed to 

 be potentially resident in the original elements of 

 which the fibrin or protein matter is composed, just 

 as the fluid property of water is to be referred to the 

 properties of its constituent gases ! But protein is 

 not contractile, nor is any variety of this passive sub- 

 stance endowed with such a property 'as that which 

 is characteristic of muscular tissue. Moreover, the 

 living matter of an amoeba or white blood-corpuscle 

 is further removed from protein than muscle itself. 

 Albumen, fibrin, and a number of other things, re- 

 sult from the death of the living matter, but it would 

 surely be deemed absurd to attribute the property of 

 living matter to the properties of the elements of the 

 materials resulting from its death, 17. Nor has 

 any one yet shown that the contractile material of 



