ANIMAL AND VEGETABLE 161 



At the risk of labouring the fact, I must repeat that the 

 tension at any point is in the inverse ratio to the surface- 

 area over which electricity is distributed. That being so 

 it follows, logically, that the tension at any point or points 

 may be varied by varying the surface-area of the conducting 

 plates, discs, or membranes. 



Sarcolemma and Neurilemma. I have classed these 

 together because, whatever differences may exist between 

 them, they have two properties in common, i.e., they are 

 both elastic and both either dielectric in character, or they 

 carry a dielectric substance or substances upon or in them. 

 If sarcolemma is not, in itself, of comparatively high 

 resistance it must carry, on its inner side, a resistant 

 substance or material, because, if it were not so carried, 

 contact might occur between the conducting plates or discs 

 or points of the sarcomeres. Also I must assume that the 

 sarcolemma is very elastic, and for this reason. Suppose 

 the sarcolemma not to exist, and that in its place was a 

 layer of dry (highly resistant) air. When an impulse was 

 sent along a motor nerve to cause contraction there would 

 be nothing to impede contraction, and the maximum 

 contractile effect would be obtained. Between this 

 unimpeded movement and movement governed by an 

 elastic material there would be a wide margin of difference 

 dependent upon the compressibility of the material 

 and Nature would adjust the degree of elasticity or com- 

 pressibility to meet requirements. 



OTHER INSULATING PROCESSES. 



Halliburton gives an illustration of a transverse section 

 of the sciatic nerve of a cat which will repay study. 



At first sight one is forcibly reminded of a number of 

 bundles of insulated wires laid in bitumen in a trough, 

 and we shall, I think, be led to the conclusion that that view 



M 



