250 Ross Granville Harrison 



with the nerves of the host. In three other cases the nerves vs^hich 

 were found were connected with the nerves of the host. With 

 reference to the other twenty-four the author does not mention 

 nerves except in two cases, in which, it is stated, the relations of 

 the nerves could not be made out. 



In a later paper Banchi gives an account of some further ex- 

 periments, in which specimens were preserved for exammation 

 at various intervals after the operation, beginning at six days. 

 The pieces transplanted were not limb buds but pieces of the side 

 of the body, including parts of myotomes and notochord and also, 

 as Banchi admits, portions of spinal nerves. Examined later, it is 

 maintained that in some cases well developed nerves may be found 

 which contain no traces of ganglion cells and have no connection 

 with the nerves of the host. Banchi concludes from these experi- 

 ments that the nerves are of pluricellular origm and that they may 

 differentiate when cut off from the center. Banchi then points 

 out that what he has found in the field of development corresponds 

 to what Bethe has found in the field of regeneration. 



These last experiments cannot be regarded as any more con- 

 clusive than the first. It must not be lost sight of that Banchi has 

 really transplanted nerves already partially differentiated; at best 

 he has shown that these nerves are able to continue their existence 

 and perhaps grow a little after being cut off from their ganglion 

 cells. But the experiments do not even prove this, for the pieces 

 were transplanted to other embryos which are teeming with nerves, 

 and in such cases there is always the possibility, or even the proba- 

 bility that connections with the nerves of the host were present but 

 overlooked. The small number of cases purporting to give positive 

 results lends strength to this view. As Braus has shown, the con- 

 necting nerves may be very much thinner than the nerves in the 

 grafted piece itself, and it is not difficult to overlook nerves of con- 

 siderable size, unless one carefully examines the series of sections 

 with an oil immersion lens. 



Gemelli's results contradict Banchi's directly and are of special 

 importance because some of the actual steps by which the ingrowth 

 of the nerves into the transplanted tissue were observed. Speci- 

 mens were killed at short intervals beginning the second day after 



