Philosophical Transactions. 381 
eases, from the greater capacity of the canal and looseness of the mem- 
branes, considerable effusion may exist, without, at first, producing any 
marked symptoms, more particularly in the lumbar region, where other cir- 
cumstances concur in rendering the effect of pressure less sensibly felt ; to 
enter into a description of which would be foreign to the object of this paper. 
5. Of the Nerves which associate the Muscles of the Chest in 
the Actions of Breathing, Speaking, and Expression ; being a 
Continuation of the Paper on the Structure and Functions of 
the Nerves. By Charles Bell, Esq. 
‘In this paper, Mr. Bell proceeds on the principle assumed 
in his former communication—that the intricacies of the nervous 
system in man depend on superadded nerves, and that through 
these, certain parts, which in the lower animals have simple 
uses, acquire additional functions. 
He shews, that when the act of respiration belongs to the 
constitution of an animal, new nerves, having a distinct centre 
or source of power, are superimposed, without deranging the 
original simple and symmetrical system which is common to 
every creature that has feeling and motion. 
He proceeds to shew, that when the act of respiration is 
performed by ribs alternately rismg and falling, the muscles 
brought into action are very numerous, and the nerves which 
combine and control the motions of the numerous and distinct 
muscles are proportionably extensive. 
He explains, in the next place, how the organs of respiration 
in man are made subject to many functions, and that hence the 
human system of respiratory nerves is more complicated than 
that of any other animal. Thus, for example, it is shewn, that 
when respiration is made subservient to speaking, singing, and 
expression, or to the mere acts of coughing, sneezing, and 
spitting, there is necessarily a combination of very distant 
parts with the simple or original act of moving the thorax, 
and that to establish these relations, new or additional nerves 
are added. 
Mr. Bell then exhibits these respiratory nerves diverging 
from a centre, and shews, by experiments, that the division of 
any one of them cuts off the parts respectively from conform- 
ing to the act of respiration; and moreover, that the injury of 
the centre or origin of these nerves deprives a person of life in 
a manner so rapid, that the agony of dying is not perceptible 
when life is thus extinguished. 
After proving the importance of these nerves to respiration, 
and consequently to life, the attention of physicians is directed . 
to the consideration of the state of this system of nerves in 
all cases of sudden death, when there is no apparent or great 
disorder of the brain or heart. 
The last part of the paper is a short developement of the 
effect of emotion on the heart, and the reflected influence of 
