THE SUPRARENAL SYSTEM 22Q 



pupil of maximal duration, while physostygmin produced myosis 

 of the normal control eye only. All that these experiments prove 

 is, that the tissue which reacts to the influence of adrenalin 

 becomes increasedly sensitive to the action of this substance after 

 decentralization, and even more so after denervation. But in the 

 case of the retractor muscle of the penis, which undoubtedly 

 possesses a double innervation, this result can hardly be due to 

 the persistence of" Fletcher's nervous network, seeing that the 

 integrity of the latter is dependent upon the nerve cells of the 

 peripheral ganglion. It is evident from this that the site of the 

 activity of adrenalin cannot be situated in the nerve endings in the 

 general sense of the term ; that is to say, in so far as they are 

 demonstrable, anatomically by methylene blue, and physiologic- 

 ally by degeneration after nervous resection. 



Upon the other hand, it is very difficult to account for the 

 effects which adrenalin has upon the unstriated muscles, and 

 especially for the different effects (contraction and relaxation) 

 which it produces upon muscles of similar structure, by the theory 

 of a direct action upon the muscles themselves. Hence, the seat 

 of the elective influence of adrenalin can only lie in the junction 

 of the sympathetic nerve-fibres with the muscles. We must, then, 

 assume that the neuro-muscular system is composed of cell, fibre, 

 and terminal derived from the nerve, and of muscle-cell and 

 contractile fibrilla derived from the muscle, and that these two 

 portions are connected by means of a third, the myoneural 

 junction. 



During the embryonal period, the muscle fibrilla possesses 

 a direct contractility only, and in certain parts of the unstriated 

 muscular structure, especially in the lower vertebrates, this 

 developmental stage persists throughout life. But in the course 

 of ontogenetic and philogenetic development, the greater number 

 of the unstriated muscles acquire a relationship to the sympathetic 

 nervous system. The myoneural junction, derived partly from 

 the muscular substance, and partly from the sympathetic nerves, 

 develops to form the mechanism which controls the manner in 

 which the muscles react in response to nervous stimuli. Whether 

 the muscle is influenced in a positive or a negative sense, whether 

 in response to such influence it contracts or relaxes, depends upon 

 the myoneural junction. Adrenalin exercises a specific stimulatory 

 effect upon this portion of the neuromuscular system, and this is 

 proved by the following facts : first, it does not influence muscles 

 which have not a sympathetic innervation (as, for instance, the 

 muscles of the bronchi) ; and second, it does not affect all muscles 

 in the same way, but produces contraction or relaxation according 

 to the nature of the myoneural junction through which it acts. 

 This specific action of adrenalin has revealed the fact, that the 

 neuro-muscular junction tissue is characteristic of the sympathetic 

 system and distinguishes it from the cranial and sacral autonomous 



