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SHOULDER ABSCESS. 
SHOULDER ABSCESS. 
Hertwig describes two varieties of shoulder abscess—-one superficial, 
consisting of inflammation of the subcutis, and only presenting the 
same features as similar swellings in other parts of the body ; another of 
a special type, almost peculiar to horses employed for draught. 
Symptoms and progress. A sharply defined, hard, slightly painful 
tumour, as large as a child’s head, lying either in or below the mastoido- 
humeralis muscle (levator humeri) suddenly appears in harness horses. 
The skin is sound and movable ; lameness is scarcely ever present, though 
Gunther states having observed it. 
For some time no marked changes occur in the swelling, except 
possibly an increase of circumference, and it remains stationary for 
weeks or months, during which steady work may be done. Usually after 
some months, fluctuation appears at the most prominent part, and on 
incision thick fluid pus is discharged. The earlier the swelling is 
punctured the more quickly it disappears. If operation is long delayed 
permanent thickening may remain. 
Opinions differ as to the origin of these tumours, though it is charac¬ 
teristic of them that soon after their formation a small suppurating point 
may always be found at their centre. 
Franck believes that they are associated with injury of the prescapular 
glands. Hertwig, who is supported by Esser, considers that they are 
caused by continuous pressure of badly-fitting collars, as indicated by 
their occurring only in draught horses, usually in those drawing heavy 
loads. Yiborg views them as complications of strangles. Every prac¬ 
titioner must have seen many draught horses with this shoulder abscess, 
but riding horses never seem to be so affected. Stockfleth, however, reports 
a case in a horse which had been confined for several months to the 
stable on account of lameness ; but this may be regarded as the exception 
which proves the rule. It is specially noteworthy that, even from their 
earliest beginning, these abscesses contain pus, in which pyogenic cocci 
are almost invariably present. This fact has been amply proved by the 
large number of these abscesses containing staphylococci opened in the 
Berlin clinique during the last few years, though streptococci were 
sometimes found instead. 
But how does the infection occur ? Though it is clear that infection 
with cocci must be associated with the mechanical-injury caused by the 
collar, it is by no means clear how the cocci penetrate to the deep-lying 
seat of abscess through uninjured skin. Schimmel urges that they pro¬ 
ceed from the lower portions of the limbs by the lymphatic vessels ; and 
in support of this view adduces the case of a horse which suffered from a 
suppurating sandcrack, from which discharge of pus was prevented 
