of the chest in breathing, speaking, and expression. 293 
more exterior division of the accessory nerve descends be- 
hind the jugular vein, and comes forward and perforates the 
mastoid muscle, (Plate XXXI. fig. II. A). In its passage 
through the muscle it sends ofFbranches which course through 
its substance ; and if, as sometimes happens, though rarely, 
the nerve does not pass through the muscle, these branches 
are, notwithstanding, invariably given to it. 
When the nerve has escaped from the back part of the 
mastoid muscle, it forms a communication with that branch of 
the 3d cervical nerve that ascends behind the muscle ; and 
nearly at the same time it is joined by a branch from the 2d 
cervical nerve. The superior respiratory nerve now descends 
upon the neck, and begins to disperse its branches in regular 
order to the edge of the trapezius muscle; (Fig. II. B.) 
four or five branches take their course to that muscle, sepa- 
rate into minute subdivisions, and are lost in its substance. 
One more considerable division, being the lowest of these, 
is joined by a long descending branch of the 2d cervical 
nerve. Encreased by this addition, it descends under the 
trapezius and behind the clavicle. Following this descending 
branch, it will be found exclusively attached to the trapezius. 
Behind the scapula it is again joined by branches from the 
spinal nerves ; and here a sort of imperfect plexus is formed, 
from which divisions of the nerve, still descending, follow 
the lower edge of the muscle, and are finally dispersed among 
its fibres. 
This nerve arises from the same column with the respira- 
tory nerves ; it takes a most intricate and circuitous passage 
to form a junction with nerves which we know to belong to 
that class ; it sends branches to join the nerves of the tongue 
