I9S JoUKNAI. OF CoMl»AKATl\E NeL'KOI.OCJY. 



4. Motor root fibres arise from large and small nerve cells 

 in all parts of the ventral cornua, each by a single nervous 

 process. 



1^. The ventral and lateral columns consist in part of 

 fibres from all regions of the cord. 



6. The greater number of longitudinal fibres of the ven- 

 tral and lateral columns give rise to lateral branches (col- 

 laterals), which enter the gray matter, especially of the 

 ventral cornua and ventral part of the dorsal cornua. 



7. All collaterals of lateral columns and nervous branches 

 of cellular processes, as well as the inflexed termini of sen- 

 sory nerves, give rise to a larger or smaller number of 

 branches, each finally form fine brushes of fibres, which col- 

 lect about nerve cells without coming into actual connection 

 with them or anastamosing with each other. 



, 8. Nerve cells of the cord are, (a) motor cells, (/>) cells 

 of the columns, (c) cells of the dorsal cornua whose nervous 

 processes do not extend beyond the gray matter, but sub- 

 divide uniformly. 



Respectingthe relation of cell and fibre, Koelliker con- 

 cludes that interaction may follow two methods: ist, direct 

 stimulation of a fibre by a cell (motor); 2nd, operation of 

 nerve fibres upon cells with which they are simply in contact 

 but are not directly connected (sensory cells). 



Voluntary motion is thus construed. Impulses conveyed 

 through pyramidal fibres pass into collaterals whose fine 

 branches are in close contact with cells of the ventral cornua 

 from which motor nerves arise. The excitement is thus im- 

 parted to these cells, and is transmitted through the nerve 

 fibres to the muscle. Koelliker considers that the motor 

 cells are collected in niduli which correspond to the 

 metameres of the body. 



Sensations, on the other hand, are conveyed by the dorsal 

 columns, but there is no evidence that they continue to the 

 cerebrum. Data derived from ascending degeneration seem 

 to indicate that these fibres end in the niduli of the medulla. 



