22 THE ELEMENTARY NERVOUS SYSTEM 



resemblance to a person suffering from complete motor 

 paralysis who might still be able to receive impressions 

 from the exterior and even to reflect on them, and yet 

 would be incapable, in consequence of the complete sep- 

 aration of nerve and muscle, of carrying out activities 

 that would maintain a harmonious adjustment with the 

 exterior. Not only does this view of the independent 

 origin of nerve and muscle meet with the inherent and 

 serious difficulty just alluded to, but among the lower 

 forms not a single animal is known in which nerve is un- 

 associated with muscle. Hence the hypothesis of Claus 

 and of Chun has received very little serious consideration. 

 Much less subject to criticism than the hypothesis of 

 the independent origin of nerve and muscle is Kleinen- 

 berg's theory of the neuromuscular cell. In 1872 Klein- 

 enberg announced the discovery in the fresh-water hydra 

 of what he designated as neuromuscular cells. The per- 

 ipheral ends of these cells were situated on the exposed 

 surface of the epithelium, of w r hich they w r ere a part and 

 were believed to act as nervous receptors ; the deep ends 

 were drawn out into muscular processes and served as 

 effectors to which transmission was supposed to be ac- 

 complished through the bodies of the cells. Each such cell 

 was regarded as a complete and independent neuromus- 

 cular mechanism, and the movements of an animal pro- 

 vided with these cells was believed to depend upon the 

 simultaneous stimulation of many such elements. It was 

 Kleinenberg's opinion that these neuromuscular cells di- 

 vided and thus gave rise to the nerve-cells and muscle- 

 cells of the higher animals. In fact, In- declared that the 

 nervous and muscular systems of these animals w r ere thus 

 to be traced back to the single type of cell, the neuromus- 

 cular cell, which morphologically and physiologically rep- 



