18 
CiAcciOj on the Distributmi of 
dividing and subdividing, pursue their courses^ the numerous 
branches resulting from their repeated division unite with 
each other. The union of one branch with another is not 
eflPected after the manner of the capillaries,, but by an inter- 
change of their respective fibres. It may be easily under- 
stood^ therefore^ that from such an arrangement a nervous 
network is formed^ with meshes varying in size as well as in 
shape^ which is interwoven with the network of the capillaries. 
I think we shall form a correct idea as to the precise manner 
in which this network is arranged, if we imagine a network 
of homogenous hyaline tubes of different sizes^ wherein nerve- 
fibres are contained, which pass alternately from one tube to 
another. 
As is shown by vertical and transverse sections, the net- 
work which has been just described is not terminal, because 
the bundles of the dark-bordered fibres, after taking part in 
its formation, pass ofiP towards the surface, crossing the middle 
layer of the derma in an almost straight direction, and with- 
out sending to it any dark-bordered fibre. As soon as they 
reach the inferior part of the outer layer of the derma, they 
again branch, and form another network exactly corresponding 
in its arrangement with the network existing in the inner 
layer. Hence two networks of dark-bordered fibres exist in 
the derma of the frog, connected together by intermedial 
bundles, one in the inner and the other in the under surface 
of the outer layer. 
Having formed this second network, the bundles of the 
dark-bordered fibres, while repeatedly dividing, continue their 
way towards the surface of the derma, are seen, sometimes 
gradually and sometimes abruptly, to loose the white sub- 
stance and to become pale nerve-fibres."": It must be here 
noted, that not all the individual fibres which enter into the 
composition of a bundle are transformed into pale fibres at 
the same time, as in some of them the transformation takes 
place sooner than in others. At the point where a dark- 
bordered fibre seems to cease, very frequently a single pale 
fibre, and sometimes more than one, can be traced in imme- 
diate continuation with it. When the dark-bordered fibres of 
every bundle have been thus transformed, they are still ob- 
served to run together in the same sheath for some distance, 
and the fibres of one bundle to pass into another, and vice 
versa. But when tliese rather large bundles of pale fibres, by 
repeatedly dividing^ are reduced in very fine bundles, then no 
appearance of sheath can be demonstrated in them. These 
exceedingly fine bundles, which are very numeroiTs, pass in 
every direction towards the surface, frequently interchanging 
