338 ELECTRO-PHYSIOLOGY CHAP. 



circumstances, be affected by the prevailing knowledge of the 

 morphology of the substrate. Appreciation of the intimate rela- 

 tion between structure and function of an element has not always 

 been as apt as could be desired, and as is indispensable to the 

 fruitful development of knowledge. The strong physical bias 

 obtaining in many minds has obscured the perception that it 

 profits little to substitute general theory and hypothesis for the 

 certain facts of histological investigation. Now, indeed, it is 

 universally accepted that histology and physiology are not two 

 independent departments of science, but are, on the contrary, 

 intimately correlated, each inspiring and attracting the other. 

 Physiology is as much concerned with histological data as with 

 those deriving from physics and chemistry. It is almost super- 

 fluous to refer to the recent developments of the cell theory, or 

 to the importance attaching to microscopic methods in general 

 muscle and nerve physiology, and in the theory of secretion. 

 The fundamental significance of an anatomical knowledge of 

 structure to the right interpretation of function has always been 

 recognised for the motor nerve - endings, and for the electrical 

 organs to be described below. 



Doyere, in 1840, was the first to observe on a micro- 

 scopic arthropod, the much -discussed Milncsium tardigradu m , 

 that the five filaments of nerve entered the muscle -fibres, 

 and apparently terminated in a conical swelling. The motor 

 nerve -en dings in striated, skeletal vertebrate muscle subse- 

 quently attracted most attention, on the one hand from purely 

 technical reasons, because it was easier to follow the more 

 coarsely-grained medullated fibres to their extreme termination, 

 on the other from the possibility of here approaching the 

 question from its physiological aspect. Frog -muscle, with its 

 nerves, has thus been the prominent if not the sole object of 

 all experiments in nerve and muscle physiology. Without 

 entering into the history of the question, we need only remark 

 that at the present time, thanks to innumerable researches, more 

 particularly those of Kiihne (53), it must be regarded as certain 

 that every striated muscle of a vertebrate possesses one or more 

 distinct nerve-endings, the structure of which is essentially similar. 

 When the medullated fibre, usually after frequent bifurcation, 

 penetrates into the muscle-fibre, its sheath of Schwann coalesces 

 with the sarcolemma, the axis-cylinder alone passing through to 





