10 BULLETIN 1470, U. S. DEPARTMENT OF AGRICULTURE 
Exterior and interior fats are firm, somewhat brittle, and white to 
slightly creamy in color. They lack the resiliency and miiky tinge 
of fat which is so pronounced in most carcasses of lamb, yet do not 
possess the same degree of hardness and brittleness of the fat usually 
found in mature mutton carcasses. 
MATURE MUTTON 
Mature mutton. — In mature mutton, the ribs show a much more 
pronounced spring or bow than is generally the case in either lamb 
or yearling mutton carcasses. This gives the sides a distended or 
barrellike appearance, particularly in the case of ewes, whereas those 
of lamb and yearling mutton are relatively straight and are more 
compact, and the general outline is more uniform and even. 
A feature which is peculiar to mature mutton carcasses is the 
appearance of the ankle joint of the forelegs. In mature mutton 
forelegs the saw-tooth effect is absent. When a lamb has passed 
through the yearling stage and has become a sheep, the cartilage 
becomes ossified or hardened and the knuckle no longer breaks off 
the end of the bone. The separation of the foot from the foreleg- 
is therefore made at the ankle joint. Thereafter the knuckle nor- 
mally forms the extreme end of the foreleg and presents a hard, 
smooth, white, shiny surface with two prominent ridges. 
Another distinguishing feature is the color of the flesh. The color 
of mutton ranges from light to dark red, compared with medium 
pink to light red in yearling mutton and light to dark pink in iamb, 
This also applies to the thin strips of lean meat extending over the 
exterior of the back and sides and somewhat broader covering of 
lean over the breast. The quantity of lean and its even distribution 
over the carcass varies according to the grade of the carcass but it is 
always visible to a greater or less extent under the fell. 1 
Wether mutton is derived from males of the ovine species which 
were castrated early in life before any marked sexual characteristics 
had developed. 
Wether mutton carcasses are distinguished from ewe mutton car- 
casses by the presence of cod fat, generally regular and more even 
conformation, a somewhat higher percentage of lean flesh to bone, 
less fat, and relatively smaller fore quarters in proportion to hind 
quarters. Both exterior and interior fats are generally less wasty 
and more evenly distributed. As a result of changes in sheep pro- 
duction which have occurred during the last quarter century rela- 
tively few wether sheep arrive at market for slaughter and there- 
fore comparatively little wether mutton is offered on consuming 
markets. The larger percentage of Choice and Prime grade mutton, 
however, is derived from wethers. 
Ewe mutton is derived from females of the ovine species which 
were at least 20 months old at time of slaughter. In most instances 
the animal has lambed one or more times. 
Carcasses of ewe mutton have relatively larger abdominal cavities 
than wethers, larger bungs and pelvic arches, and smaller necks and 
shanks. The presence in ewe-mutton carcasses of parts of the udder 
is also a distinguishing feature. The bones are generally harder 
1 The fell is a thin, tough membrane covering the carcass immediately under the pelt. 
It should be removed before cooking. 
