140 The Alligator and Its Allies 
the serratus superficialis and the hinder regions 
of the collo-thoraci-suprascapularis profundus 
muscles, unites with the tenth nerve just after 
giving off the small thoracicus inferior nerve 
to the costo-coracoideus muscle. After uniting 
with the tenth nerve the ninth nerve immediately 
divides into two branches that form loops with 
branches of the eighth nerve, the whole making a 
very complicated plexus. 
X. The tenth nerve, as noted above, is one of 
the two largest nerves of the brachial plexus. 
After giving off a single nerve to the ventral 
musculature, this nerve unites with the eleventh 
nerve; it then gives a branch to the costo-coracoid- 
eus muscle and forms a loop with the ninth nerve. 
After giving off a couple of nerves it again divides 
into two equal branches which unite with similar 
branches of the eighth nerve. 
XI. The eleventh nerve is next to the smallest 
of the plexus. Besides branches to the trunk 
musculature it gives a fine twig to the integument 
of the axilla and unites with the tenth nerve in the 
brachial plexus. This is the last nerve that enters 
into the brachial plexus. 
The distribution of the nerves of the brachial 
plexus is as follows (Fig. 31): (a) supracoracoideus 
to the muscle of that name and to the integument 
of the breast; (b) thoraci inferiores nerves (10a)— 
a complex of nerves from the eighth, ninth, and 
tenth spinal stems—lead to the costo-coracoideus 
