238 PROCEEDINGS OF THE AMERICAN ACADEMY. 



heiten (Neuronen)." Von Lenhossek ('95) declares the principle of the 

 neuron to be true for invertebrates as well as vertebrates. He says 

 ('95, p. 108) : " Auch bei den wirbellosen Tieren setzt sich das Nerven- 

 system aus Neuren zusammen." Later (p. 109) he says: " Nervenfaser, 

 Terminalverjistelung und Seitenzweige stellen leitende Medien, Aus- 

 wiichse des Zellkorpers dar, die dieser dem Bedlirfnisse entsprechend 

 entwickelt, zu nahe und entfernt von ihm gelegenen Elementen Bezieh- 

 ungen einzugehen : andere Nervenzellen zu umspinnen, in sensible 

 Endbezirke hineinzurageu oder sich an kontraktile Elemente anzuloten. 

 Diese Beziehungen bestehen stets in einem innigen Kontakt. Darin liegt 

 ein wichtiges Organisationsgesetz, nicht nur fiir die hoheren Lebewesen, 

 sondern auch fiir die wirbellosen Tiere, bis zu der Lebensstufe hinunter, 

 wo die erste Nerveuzelle und Nervenfaser in die Erscheinung tritt." 



But in the case of Leydig's fibre, the entire weight of evidence is 

 to the effect that we have direct continuity of substance, not simply inti- 

 mate contact, between the processes of different nerve cells. I am aware 

 that a zealous supporter of the neuron theory might claim that, although 

 the individual cell-processes lost their respective sheaths on entering 

 Leydig's fibre, still each process remained distinct and maintained its 

 individuality, — that Leydig's fibre was simply a bundle oi distinct nerve 

 processes extending side by side, but closely pressed together. The 

 evidence offered by the work of Cerfontaine ('92) with methylen blue is, 

 however, entirely against such a supposition. Every worker with me- 

 thylen blue as an intra vitam stain knows its tendency to pick out and 

 stain a few nerve cells and nerve fibres. But the results obtained by 

 Cerfontaine gave no evidence that parts of the fibre were selected by this 

 stain and others left unstained, as would almost certainly be the case if 

 it were composed of physiologically distinct strands or tracts. His fig- 

 ures show that Leydig's fibre, when treated with methylen blue, is a 

 single homogeneous structure. 



I regret that I have not had time and opportunity to experiment with 

 the action of methylen blue upon these structures. But I believe that 

 the facts already presented prove that there is no separation or boundary 

 between ^these particular cell processes. But if there is no discoverable 

 boundary, it is highly improbable that the processes retain their individu- 

 ality and physiological independence. Leydig's fibre seems to be an 

 effective means of bringing about an intermingling of the substance of 

 these processes. The anastomosing of the different Leydig's fibres which 

 Friedlaender and Cerfontaine describe in case of Lumbricus is another 

 condition which harmonizes with this interpretation. 



