724 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
and different species. In the homo-transplanted series there was no new axis-cylinder 
formation, as the apotrophic cells were present only in small numbers, and in the 
hetero-transplanted series the grafts were entirely removed by phagocytosis on the 
part of polymorpho-nuclear cells—just as the blood corpuscles of one animal are 
destroyed by the body fluids of an animal of another species. 
PrrRrRoncito (1907) divided the sciatic nerve in dogs, and observed, by means of 
Cajal’s reduced silver method, the changes which occur from the very earliest period 
onwards. He was the first to show that the signs of regeneration described by Casau 
occur very early. Twenty-four hours after section PERRoNcrITO found traces of collateral 
and terminal ramifications, and already, in two days, newly-formed fibres which spring 
from the central stump have reached the scar-tissue and show a very fine fibrillar 
structure, with end thickenings and terminal balls. He has also described a process 
of the unravelling of the thickened central end axis-cylinder which precedes the 
development of the new fibres, an appearance which Cagat has termed “ the phenomenon 
of Perroncito.” Axis-cylinders may later grow out as compact axis-cylinders, become 
dissociated into fibrils, and unite again into a compact axis-cylinder. On the tenth day 
after section the connection between the separated ends of a non-united nerve is com- 
pleted by newly-formed fibres, many of which show forkings with terminal balls. 
PrrRoncito also draws attention to the length of time that old axis-cylinders may be 
recognised in the peripheral stump, and concludes that they are non-medullated or 
Remak’s fibres. 
Casa (1904-1907).—It is impossible in a short review to do justice to the work of 
Casa, which has been the source of inspiration to so many. It is the less necessary to 
attempt this, as many of his beautiful illustrations, showing stages in the regeneration 
of the axis-cylinder, are reproduced in the more recent text-books, and all are familiar 
with his terms—céne de croissance, massue de croissance, and boules terminales. As 
in the early development, so in the genesis of the new fibres in regeneration the work 
of CasaL was the first that seriously opposed the new teaching that set in with Von 
BUNGNER’S researches and that seemed destined to replace the outgrowth theory. This 
reaction in favour of the outgrowth theory must be associated with the names of Casau, 
Perroncito, and Lugaro. It need therefore scarcely be added that Casat’s researches 
have demonstrated that the nerve fibres of the scar-tissue and peripheral end are always 
formed by growth from the central end. In the peripheral segment near the cut portion, 
preceding the degeneration of the axis-cylinder, Casau noted signs of regeneration— 
indicating that the axis-cylinders do not die immediately that they are cut off from 
their trophic centres, but that during the short period of their survival they attempt 
regeneration. By the eighth day all the axis-cylinders in the peripheral segment have 
undergone a granular degeneration except the fibres of Remak, which resist longer, 
In the central end the axons commence to modify on the first day, the first 
change being a terminals massue de croissance, from which filaments proceed ;: other 
axons show a reticulated or dissociated appearance. ‘The filaments and the dissociated 
