2(i4 
ANIMAL PATHOLOGY. 
muscle, like the trapezius, has other nerves which constitute it 
a voluntary motor muscle ; but the long descending nerve consti- 
tutes it an organic muscle, in order to contribute to the produc- 
tion of full inspiration. 
The Intercostal and Lumbar Nerves belong to precisely the 
same class. They are all nerves of voluntary motion and sen- 
sation. By means of the proper intercostals, whether external 
or internal, the costal arches are brought forwards and thrown 
outwards, and thus the cavity of the chest is enlarged. Being 
the muscles of the sternal region, they approximate the cartilages 
of the anterior ribs, they elevate perhaps in some measure the ster- 
num, and they contract the cavity of the chest. The dorso-costai 
muscles elevate the ribs, and enlarge the cavity of the chest — 
the levatores do so more especially. All the external abdominal 
muscles, while they support different parts of the viscera, while 
they compress the bowels, and assist in the evacuation of the 
faeces and of urine, act exceeding powerfully in diminishing the 
cavity of the chest, whether longitudinally or laterally. These 
are all muscles of voluntary power — we often use them forcibly 
and effectually for several purposes ; but they are also — the 
greater part, or the whole of them — muscles of involuntary 
power — muscles connected with organic life. They are therefore 
not only made up of fibres from what we have hitherto been accus- 
tomed to consider as the only powers resident in the spinal cord, 
feeling and voluntary motion : they are acted upon by other 
principles, they are devoted to other purposes ; they are parcels 
and portions of that system of organic and vital power which first 
began to be evidently developed in the medulla oblongata, but 
pervades the greater part of the spinal system, and is the most 
important part of it. 
The Lxcito-motorij System . — These powers of the organic 
nerves, attached to and forming a part and portion of the spinal 
cord, although not yet demonstratively proved to have bodily ex- 
istence there by means of the anatomist’s knife, yet are suffi- 
ciently and satisfactorily proved by their incessant and powerful 
agency. The functions of life are discharged by their energy, 
and by that alone, and while we are altogether unconscious of 
the affair : they belong to the system of organic life. The nerves to 
which almost alone attention has been directed, are the sentient 
and the voluntary, so these, by some physiologists, are divided into 
the excitor and the motory. The first, or the excitor nerves, pur- 
sue their course principally from internal surfaces, characterized 
by peculiar excitabilities to the true medulla oblongata, or spinal 
cord : the second, or the motor nerves, pursue a reflex course from 
that medulla to muscles having peculiar actions, and principally 
