of the chest in breathing , speakbig , and expression. 289 
breathing is exhibited in gasping and forcible inspiration, in 
drawing the breath, not in throwing it out. 
Accordingly, when we examine the trunk of the human 
body, we have no difficulty in distinguishing the muscles most 
capable of raising the chest ; and these in effect, we see power- 
fully influenced in deep inspiration, whether the action be 
voluntary, as in speech, or involuntary, as in the last efforts 
of life, when sense is lost. They are the mastoid muscle, 
the trapezius, the serratus magnus, and the diaphragm. 
1. Sterno-cleido-mastoideus .* This muscle, by its attach- 
ment to the sternum or breast bone, raises or heaves the 
chest ; and the operation of this muscle is very evident in all 
excited states of respiration, in speaking, and still more in sing- 
ing, coughing, and sneezing. But there is something neces- 
sary to the full effect of this muscle on the chest, for other- 
wise it will be a muscle of the head, and not of the chest. 
2. The trapezius •f must fix the head or pull it backwards 
before the mastoideus can act as a respiratory muscle, and how 
they are combined we shall presently see. The position of 
the head of the asthmatic, during the fit, as well as the pos* 
ture of the wounded or the dying, prove the influence of the 
upper part of the trapezius in excited respiration. 
The trapezius has a still more powerful and important in- 
fluence in respiration when the action rises above the ordi- 
nary condition, and that is by drawing back the scapula, to 
give the necessary effect to the action of the serratus magnus. 
3. The serratus magnus anticus £ being extended over the 
whole side of the chest, and attached in all the extent from 
the second to the eighth rib, is very powerful in raising the 
* See Plate XXXI. fig. 2, A. f Fig. 2, B. B. J Fig. 2, E. E, 
p P 
MDCCCXXII. 
