246 
SIR CHARLES BELL ON THE NERVOUS SYSTEM. 
tion, I have met with no instance of disease in the bodies of the vertebrae attended 
with paraplegia, in which the muscular power of the limbs has not been the first 
affected : in all, the defect of motion has been greater than the diminution of sensi- 
bility ; in some, the motion of the limbs has been lost, whilst the sensibility has been 
exquisitely acute. 
These facts, it is now obvious, are to be accounted for by the motor roots of the 
spinal nerves being more directly exposed to the influence of the inflammation seated 
in the bodies of the vertebrae, than the posterior roots of sensation, which arise more 
remote from the disease. 
In a case now before me, there is disease affecting the bodies of the vertebrae of 
the neck; the arms hang powerless, whilst the sensibility is perfect; and the patient 
walks stoutly. By looking to the roots of the great nerves of the axillary plexus, in 
the dead body, the cause of this is manifest ; we see that the motor roots cover the 
spinal marrow, and that, whilst they protect the body of the spinal marrow, they are 
exposed themselves, by their proximity, to participate in the inflammation of the bone. 
When a section of the spine and sheath of the spinal marrow is made, especially in 
the neck or in the loins, it is observed that not only do the anterior roots of the 
nerves protect the column of the spinal marrow from which they arise, but these 
roots, together with the ligamenta denticulata , whilst they are themselves exposed to 
the influence of disease in the bodies of the vertebrae, guard the posterior column 
and sensitive roots. If the inflammation or morbid influence, in this case, had pene- 
trated to the spinal marrrow, and had paralysed the muscles of the upper extremities, 
by affecting that organ, the muscles of the lower extremities would have suffered 
equally with those of the upper. 
The spinal marrow, properly speaking, terminates at the second lumbar vertebra : 
but the anterior roots of the nerves forming the cauda equina , cover and protect the 
posterior roots from the influence of disease in the bodies of the vertebrae. 
The following occurrence will be regarded with interest in connexion with this 
subject. Plate IX. exhibits a tumour which engaged the anterior roots of the sacral 
nerves, as they form the cauda equina within the tube of the vertebrae. The tumour 
was of the form of an almond, but larger, and into it, the motor roots, both of the 
right and left side, were gathered, whilst the sensitive roots were free. The peculiar 
circumstances attending the case were communicated to me while the patient, who 
was in the public hospital of Edinburgh, was alive. The lower extremities were de- 
prived of motion, whilst they retained sensibility; and symptoms of so much interest 
were noted and discussed by the physicians and pupils. 
When a tumour on a nerve interrupts the communication between the brain and 
the extremity of the nerve, and the consequences are observed, they are conclusive 
as to the functions of that nerve, and afford a proof of them much superior to expe- 
riment. When a case of disease in the fifth nerve of the brain presents itself, the 
insensibility of the side of the tongue, of the side of the face and head, and of all the 
