422 SCIENCE PROGRESS 



olive-shaped swelling at the free end of each growing axis- 

 cylinder. These are also figured by Marinesco, and I am 

 indebted to the kindness of Prof. Marinesco for figures i and 

 2, which illustrate these swellings ; in figure 2 the convo- 

 luted course of the new fibres, which is so frequently seen, is 

 shown. 



Marinesco calls attention also to the fact that these terminal 

 swellings, although they may roughly be described as olive- 

 shaped, vary a good deal in external form ; this is shown in 

 the drawings, and is quite intelligible now that we have Ross 

 Harrison's description of the constant changes of form the}' 

 exhibit in embryonic history. In regenerating fibres we have 

 not direct evidence that similar amoeboid movements take 

 place, for the preparations were made not while the fibres 

 possessed vitality but after fixation with a suitable hardening 

 reagent. Still, the mere fact that they are fixed in various 

 shapes is conclusive evidence that they do exhibit these 

 changing outlines. 



Marinesco has passed through the stage so often seen 

 in those who have attacked the problem of nerve repair. In 

 his earlier publications he thought his preparations afforded 

 evidence of auto-regeneration, though he never went as far as 

 Bethe has done in that direction. In his latest papers he has 

 entirely recanted these views, and is now convinced that auto- 

 regeneration is a myth. I reproduce two more of his very 

 beautiful illustrations. The preparations were stained by Cajal's 

 new method, and they require but little comment. 



They show the new fibres penetrating the cicatricial tissue 

 of the junction from the central end in a peripheral direction; 

 they show the absence of any new axons developed auto- 

 genetically in the peripheral end. Such preparations ought to 

 carry conviction to those who have any lingering belief in auto- 

 regeneration, that the Wallerian view is the only possible one 

 to adopt. 



It must not, however, be supposed that the peripheral end 

 is entirely inactive ; for while degeneration is progressing in 

 the axons and their fatty sheath, an active multiplication oi 

 the cells of the primitive sheath or neurilemma is taking place. 

 These neurilemmal cells probably play a nutritive action 

 towards the more important structures within them, and Graham 

 Kerr, in a recent study of nerve growth in the fish Lcpidosurn, 



