366 DISEASES OF THE HORSE. 
articulated in a comparatively loose manner with the bone of the arm, 
but the joint is, notwithstanding, rather solid, and is powerfully 
strengthened by tendons passing outside, inside, and in front of it. 
Still, shoulder lameness or sprain may exist, originating in lacera- 
tions of the muscles, the tendons or the ligaments of the joint, or 
perhaps in diseases of the bones themselves. “Slip of the shoulder” 
is a phrase frequently applied to such lesions. 
The identification of the particular structures involved in these 
lesions is of much importance, in view of its bearing upon the ques- 
tion of prognosis. For example, while a simple superficial injury of 
the spinatus muscles, or the muscles by which the leg is attached to 
the trunk, may not be of serious import and may readily yield to 
treatment, or even recover spontaneously and without interference, 
the condition is quite changed in a case of tearing of the flexor 
brachii, or of its tendons as they pass in front of the articulation, or, 
what is still more serious, if there is inflammation or ulceration in the 
groove over which this tendon slides, or upon the articular surfaces 
or their surroundings, or periostitis at any point adjacent. 
Causes.—The frequency of attacks of shoulder lameness is not diffi- 
cult to account for. The superficial and unprotected position of the 
part and the numerous movements of which it is capable, and which, 
in fact, it performs, render it both subjectively and objectively pre- 
eminently liable to accident or injury. It would be difficult and 
would not materially avail to enumerate all the forms of violence by 
which the shoulder may be crippled. A fall, accompanied with pow- 
erful concussion ; a violent muscular contraction in starting a heavily 
loaded vehicle from a standstill; a misstep following a quick muscular 
effort; a jump accompanied with miscalculated results in alighting; a 
slip on a smooth, icy road; balling the feet with snow; colliding with 
another horse or other object—indeed, the list may be indefinitely 
extended, but without profit or utility. 
Symptoms.—Some of the symptoms of shoulder lameness are pecu- 
liar to themselves, and yet the trouble is frequently mistaken for 
other affections—navicular disease more often than any other. The 
fact that in both affections there are instances when the external 
symptoms are but imperfectly defined, and that one of them especially 
is very similar in both, is sufficient to mislead careless or inexperienced 
observers and to occasion the error which is sometimes committed of 
applying to one disease the name of the other, erring both ways in the 
interchange. The true designation of pathological lesions is very far 
at times from being of certain and easy accomplishment, and, owing 
to the massive structure of the parts we are considering, this is es- 
pecially true in the present connection. Still there are many cases in 
which there is really no reasonable excuse for an error in diagnosis by 
an average practitioner. 
