182 



PHYSIOLOGY 



CHAP. 



the neuroblasts gradually move away from the wall of the neural 

 canal towards the exterior. Many of them remain in the central 

 grey matter ; others wander out to form the cerebrospinal ganglia, 

 sympathetic ganglia, etc. 



But this theory of His, in so far as it conceives the nerves 

 to be only appendages of the ganglion cells, is contradicted by 

 the observations of Balfour, Beard, Dohrn, Kupfer, and Eaffaele 



FIG. IIP. Cerebellar cortex showing relations between the small cells of the molecular layer and 

 the body of Pnrkinje's cells. (Golgi.) The nerve-fibres descending from the small cells of the 

 molecular layer partially embrace the large body of the Purkinje cells, partially pass between 

 these, and then subdivide repeatedly belowjthem to form another diffuse network 



on fishes, and the more recent work of Bethe, Paladiuo, Fragnito, 

 and Capobianco on chick embryos. According to these observers 

 the axis - cylinders of the peripheral nerves and of the white 

 matter of the central organs are not (from the histogenetical 

 point of view) composed of prolongations of the axons and 

 dendrites of the ganglion cells, but are derived from the fusion 

 of many cells arranged in series, and only contract relations with 

 the ganglion cells at a later time. The problem is still unsolved, 

 since some authors (Harrison in the first place) confirm the 

 view of His, while others take the polygenetic theory as proven. 



