246 PHYSIOLOGY or muscles axd xekves. 



what different ; but the relation between the nerve and 

 the muscle is the same. The essential fact is the same 

 in all cases : the nerve ^^a-s'ses into direct contact 

 ivith the muscle-suhstance. All observers are now 

 agreed on this point. Uncertainty prevails only as to 

 the further nature of the terminal plate. In the frog, 

 for instance, there is no real terminal plate, but the 

 nerve separates within the sarcolemma into a net-like 

 series of branches, which can be traced for a short dis- 

 tance from the point of entrance in both directions. 

 Professor Gerlach has recently declared that this net, 

 as well as the terminal nerve-plate, are not really the 

 ends of the nerves, but that the nerve penetrates 

 throughout the muscle-substance, and that throughout 

 the whole muscle-fibre there is an intimate union of 

 nerve and muscle. 



2. However this may be, the fact that the nerve- 

 substance and the muscle-substance are in immediate 

 contact must serve as the starting-point from which to 

 attempt an explanation. When it was thought that 

 the nerve remained on the outer surface of the muscle- 

 fibre, there was difficulty in explaining how a pulsation 

 of individual muscle-fibres within a muscle could be 

 elicited by irritation of individual fibres of a nerve. 

 For the nerve-fibres, in their course within the muscle, 

 touch externally many muscle-fibres, over which they 

 pass before they finally end at another muscle-fibre. 

 In the case of flat, thin muscles, it may be shown con- 

 clusively that such a nerve-fibre may be irritated in 

 such a way that those muscle-fibres over which it 

 passes remain quiescent, and only those pulsate at 

 which the nerve-fibre ends. As soon, however, as it is 

 understood that the excitement present in the nerve- 



