TRAUMATIC LESIONS. 385 
ous in nature, hypertrophical or atrophical, specially when other causes 
occur ulteriorly, some of which are known—traumatisms, infections—and. 
others remain unknown. In the field of distribution of a divided 
nerve, no organ or tissue is surely exempt from it. They have been 
observed, specially in the skin, cellular tissues, tendons, bones and 
articulations. Their mode of production is only imperfectly known, but 
in animals, no more than in man, subsequent traumatisms do not seem 
mecessary to their production. On this point, clinical observation and ex- 
perimentation agree. If, says Lancereaux, the production of lesions “is 
assisted by a traumatism or any irritation of the tissues, it must be acknow- 
ledged that this circumstance is not absolutely necessary and that some 
times gangrene occurs entirely without any special occasional cause.” 
Quite recently, in a horse upon which, two years ago, we had divided the 
external plantar nerve above the fetlock, we have seen appear, without 
any traumatism, serious lesions which condemned him to be destroyed. 
Brown-Séquard and other observers, who have studied the effects of the 
section of the sciatic nerve, have not always seen the leg remaining zademne, 
as some pretend; in several animals, they have seen numerous trophical 
troubles, specially gangrene of the extremity and sloughing of the 
phalanges. 
The compression of nerves has causes whose action is either sudden or 
slow. One understands that the evolution of the troubles will differ 
whether the compression is produced severely at once in the middle of a 
traumatic center or realized gradually by a neoplasm developing in 
proximity of a nervous cord. On animals kept in decubital position for a 
long time, specially when a leg is secured in crossed position, a more or 
less complete impotency of the displaced leg is sometimes observed, due 
as it is to the compression of the brachial plexus between the arm and the 
trunk. After some dystokias, when powerful tractions have been made to 
remove a foetus of abnormal size, out of proportion with the dimensions 
of the canal through which it has to pass, one may frequently observe, in the 
cow especially, a lameness due to compression of the obturator nerve (see 
Paralysis). Accidents of similar order brought on by the compression 
of the gluteal nerve or of the great femoro-poplitial, have been observed. 
The application of cords and hooks may produce, in the foetus, various 
paralysis yet little studied. Traumatic lesions, inflammatory exudates, 
large cicatrices, tumors, exostosis are as many causes of compression of 
nerves. At the post-mortem of a horse, affected with incurable lameness, 
Rigot found, at the point of insertion of the tendon common to the great 
dorsal and the long adductor of the arm, an irregular exostosis, which 
had injured some of the nerves of the brachial plexus; “the neurilemna 
and pulp of these nerves was of a dark-wine color.” When the com— 
