KINDS OF PROTOPLASM. 



traction of muscular tissue. In the first, movements occur 

 in every direction, while the last is characterized by a repe- 

 tition of movement in two definite directions only. And 

 when we come to study the matter which is the seat of these 

 two kinds of movements respectively, we find very im- 

 portant differences. The matter of the amoeba, white 

 blood-corpuscle, &c., grows. It takes up matter unlike itself, 

 and communicates to it its own properties. Now, muscular 

 tissue does not do this. In short, the first kind of matter 

 acts and moves of itself; but the last can only be acted 

 upon and made to move. The first may be compared with a 

 spring, as yet undiscovered, which not only winds itself up 

 and uncoils, but every part of which moves in any direc- 

 tion, and can make new springs out of matter which has 

 none of the properties of a spring j the last with a spring 

 which can only uncoil itself after it has been wound up. 



Further, the term protoplasm has not been applied only 

 to the matter of which the amoeba, the sarcode of the fora- 

 aninifera, &c., is composed, and that which constitutes the 

 ^white blood-corpuscle and such bodies, but the matter 

 which is gradually assuming the form of tissue has been 

 considered to be of the same nature. The radiating fibres 

 of the caudate nerve-cells of the spinal cord have been 

 termed protoplasm fibres, and the outer part of the nerve- 

 cell with which they are continuous is composed of the 

 same substance. The axis cylinder of the dark-bordered 

 nerve-fibres and the fine ultimate nerve-fibres in peripheral 

 parts have been looked upon as a form of protoplasm ; but 

 it is hardly necessary to remark that, whatever may be the 

 nature of the material of which nerve-fibres and the outer 

 part of nerve-cells are composed 4 it possesses properties 



