WAITE: PLEXI OF NECTURUS. 18 
Nerve ı (Fig. 1) is slender, and does not contribute to the innerva- 
tion of the appendage, but is distributed to the inner wall of the girdle. 
It often lies close to nerve 11, and may (six cases in thirty) anastomose 
with it. 
Nerve 11 is also slender, and is distributed to the same region as is 1. 
It seems questionable if 1 and 1 can be properly considered parts of the 
plexus. In strength they approximate the ordinary post-brachial spinal 
nerves (vi to xv). In some cases branches of 11 run in close relation to 
the supracoracoid (su'erac.) branch of 11, and may (four cases in thirty) 
pass out through the coracoid foramen with the supracoracoid. In no 
case have I found any anastomosis between branches of 11 and 111, as im- 
plied by Hoffman (’74, p. 229) in his account of Necturus (Menobranchus); 
and from my specimens of Necturus I can assert that this is certainly 
not a constant relation, if indeed it occur at all. 
Nerve 11 usually divides into three branches, of which the small 
anterior one is distributed to the thoracic wall, the middle one forms the 
supracoracoid nerve (swerac.), while the larger posterior branch enters 
the main trunk of the plexus. 
Nerve ıv is usually the strongest trunk of the plexus. It passes 
directly to its exit posterior to the scapula, close to the margin of the 
glenoid cavity, giving off in its course a single small branch, which is 
distributed anteriorly on the thoracic wall. Before reaching the border 
of the scapula this nerve usually divides into two main branches, which 
pass side by side to the musculature of the anterior appendage. 
Nerve v is the most posterior nerve to enter the plexus, its anterior 
branch joining nerve 1v just before this reaches the scapula, while the 
small median and the posterior branches are distributed to the body wall, 
posterior to the girdle. 
There were no variations of note in the topography of the plexi in the 
thirty animals examined, except in one case of slight want of symmetry in 
the point of junction of v with tv, but this occurred in a specimen which 
was normal in its sacral structures. Some variation occurs in the rela- 
tive strengths of the nerves ; for while 1v is usually the strongest, it may 
be equalled by 111, as was seen in six cases, of which four were with the 
sacrum in a normal position (19th vertebra), one with the sacrum on 
the 20th vertebra, and one with an unsymmetrical sacrum (Plate 2, 
Fig. 5). Again, nerves 111 and v are usually of about equal strength, 
but ım may be much (six to eight timos) stronger than v, or more 
rarely may be weaker. 
These conditions show a tendency toward variation in the location of 
