74
F. B. SHORLAND
pasture-fed animals. The fatty tissue, muscle, and liver samples are
from the same animals, whereas the hoof and bone oils were taken
from animals in the same district and are probably comparable. The
mesenteric fat, however, is from a pasture-fed horse in England.
The composition of the fats is much more alike in the horse than
in the fats from the diiferent parts of sheep and oxen, and there appears
to be little, if any, change in the contents of either stearic or palmitoleic
acids. The hoof oils, however, show, as in oxen, a decreased content of
palmitic and stearic acid, which is largely compensated for by the rise
in palmitoleic acid.
C. FATTY ACIDS OF MILK FATS
Investigations on milk fats, especially of ruminants, have revealed
that they are derived mainly by synthesis from acetate in the udder,
though the dietary fatty acids contribute to some extent [cf. Shorland
(89)]. The synthetic activity of the mammary tissues leads to the
formation of volatile fatty acids which appear to a varying degree in the
milk fats of animals.
The milk fats of ruminants, including those of the cow, buffalo, goat,
camel, and sheep [cf. Hilditch (3)] are notable for their high contents
of lower (C 4 -C 10 ) saturated acids (see Table XXVII). The fatty acid
composition of these fats is generally similar, but cow milk fats have a
somewhat higher content of butyric acid. On the other hand, the goat
and sheep milk fats are notably rich in decanoic acid (about 10 moles %
as compared with 2-3 moles % found in cow milk fat). The presence of
these high proportions of volatile fatty acids gives to the ruminant milk
fats a characteristic feature that differentiates them from the corresponding depot fats in which these acids are not present in more than
trace amounts. In the horse and human milk fats lower volatile fatty
acids are also present, but in much lesser amounts, so that they are
more like depot fats than are the ruminant milk fats. Sow milk fat
resembles fairly closely pig depot fats, and the milk fats of seals and
whales, in which the lower volatile acids are absent, are virtually indistinguishable from a typical marine mammalian depot fat.
The results given in Table XXVII are based on ester-fractionation
techniques which do not readily reveal the traces of n-odd numbered
and branched-chain fatty acids now known to occur in ruminant milk
fats (332a). These constituents have also been revealed in human milk
fats by use of gas-liquid chromatography (332b).
D. THE FATTY ACIDS OF SEBUM AND HAIR
The best-known of these secretions is wool wax, the fatty acid composition of which has been elucidated only within the past fifteen
F. B. SHORLAND
pasture-fed animals. The fatty tissue, muscle, and liver samples are
from the same animals, whereas the hoof and bone oils were taken
from animals in the same district and are probably comparable. The
mesenteric fat, however, is from a pasture-fed horse in England.
The composition of the fats is much more alike in the horse than
in the fats from the diiferent parts of sheep and oxen, and there appears
to be little, if any, change in the contents of either stearic or palmitoleic
acids. The hoof oils, however, show, as in oxen, a decreased content of
palmitic and stearic acid, which is largely compensated for by the rise
in palmitoleic acid.
C. FATTY ACIDS OF MILK FATS
Investigations on milk fats, especially of ruminants, have revealed
that they are derived mainly by synthesis from acetate in the udder,
though the dietary fatty acids contribute to some extent [cf. Shorland
(89)]. The synthetic activity of the mammary tissues leads to the
formation of volatile fatty acids which appear to a varying degree in the
milk fats of animals.
The milk fats of ruminants, including those of the cow, buffalo, goat,
camel, and sheep [cf. Hilditch (3)] are notable for their high contents
of lower (C 4 -C 10 ) saturated acids (see Table XXVII). The fatty acid
composition of these fats is generally similar, but cow milk fats have a
somewhat higher content of butyric acid. On the other hand, the goat
and sheep milk fats are notably rich in decanoic acid (about 10 moles %
as compared with 2-3 moles % found in cow milk fat). The presence of
these high proportions of volatile fatty acids gives to the ruminant milk
fats a characteristic feature that differentiates them from the corresponding depot fats in which these acids are not present in more than
trace amounts. In the horse and human milk fats lower volatile fatty
acids are also present, but in much lesser amounts, so that they are
more like depot fats than are the ruminant milk fats. Sow milk fat
resembles fairly closely pig depot fats, and the milk fats of seals and
whales, in which the lower volatile acids are absent, are virtually indistinguishable from a typical marine mammalian depot fat.
The results given in Table XXVII are based on ester-fractionation
techniques which do not readily reveal the traces of n-odd numbered
and branched-chain fatty acids now known to occur in ruminant milk
fats (332a). These constituents have also been revealed in human milk
fats by use of gas-liquid chromatography (332b).
D. THE FATTY ACIDS OF SEBUM AND HAIR
The best-known of these secretions is wool wax, the fatty acid composition of which has been elucidated only within the past fifteen