152 KIYOYASU MARUI 



fibril net-work of the nerve cell in two difTerent ways. In one 

 group of the terminal feet the net-work is connected with the intra- 

 cellular neurofibrils by means of a feebly stained neurofibril net- 

 work, embedded in a homogeneous substance, and in the other 

 group delicate neurofibrils enter the cell body from the terminal 

 feet in a radial direction, also surrounded by homogeneous ma- 

 terial. Holmgren (22) distinguished also two types of terminal 

 feet; his first type was of annular shape and his second type 

 showed a tiny net-work, which is connected directly with the 

 neurofibril net of the nerve cell. Later Cajal (13) also figured 

 and described net-shaped terminal and transitional knobs and 

 minute ring-shaped structures, which he believed to come into 

 contact with the cell surface. Heidenhain (11) declared even 

 that these are nothing but the net corpuscles, which appear in 

 the peripheral nerve endings. In my Cajal preparations, how- 

 ever, the net-like structure of these nerve endings, as remarked, 

 did never come to my observation. Some of the terminal feet 

 looked merely granular in my preparations, owing to a fine silver 

 precipitate; occasionally I observed in them a false net figure 

 caused by the irregular distribution of the latter. But the pic- 

 tures which are shown in figure 8 exclude beyond doubt the net 

 figure of the 'bontones.' I wonder if the terminal feet possess 

 really the net structure, as it was claimed by Held (19, 20), 

 Holmgren (22), Cajal (13), and others. I suppose that this net 

 figure comes from artificial admixtures of the impregnation of 

 the honeycomb structure of the neuroplasm, which occurs now 

 and then in Cajal' s technic. To this question I shall return 

 later. 



As far as my observations go, the terminal feet must not be 

 regarded as the definite ends of the axone fibers, as was assumed 

 by Cajal and others. In my Cajal preparations I observed very 

 often that single or multiple delicate neurofibrils come from the 

 end of the terminal feet and advance toward the cell surface, 

 embedded in a homogeneous substance and entering the cell 

 body (fig. 12). I am very sorry to confess, however, that I 

 could not demonstrate definitely the neurofibril continuity in 



