1. FATTY ACID OCCURRENCE AND DISTRIBUTION
71
nephric and outer back fats results, in accordance with Hilditch's views,
from an exchange in the proportions of stearic and oleic acids.
In cattle, however, Dahl (318) considers that the differences between
the perinephric and external tissue fats arise from changes in the proportions of palmitoleic and stearic acid. This view is supported by the
analysis of an ox brisket fat, which shows about 17% palmitoleic acid as
compared with less than 2% normally present in the perinephric fat. It
is also supported to some extent by the work of Shorland and Hansen
(319) (see Table XXIV), though here the external tissue fat, as compared with the kidney fat, contains more oleic as well as palmitoleic acid
to compensate for the reduced proportions of stearic acid. In the New
Zealand sample of external tissue fat the stearic acid content is still
relatively high (13.4%) as compared with only 5.4% found by Dahl
(318). It is possible in the colder climates that the external tissue fats
are more unsaturated and contain less stearic acid. This accords with
the findings for pigs of Henriques and Hansen (322) where they show
that the iodine value is related to the temperature at the site of fat
deposition. It is conceivable that if the stearic acid content of the New
Zealand sample were lower the palmitoleic acid content would be
more in line with that found by Dahl (318).
The yellow marrow fat of the bone appears to correspond in its fatty
acid composition to that of other depot fats, whereas neatsfoot oil prepared from the hoofs of oxen is low both in stearic acid and palmitic
acid. Here the liquid nature of the fat is due to the high content of
both oleic and palmitoleic acids. In the liver glycerides the content of
palmitic acid is also low but is compensated for not by palmitoleic, but
by C 20 and C 22 highly unsaturated acids.
In the sheep the variations between the external tissue fats and
the perinephric fats, as in the pig, are largely the result of an exchange
between oleic and stearic acids (see Table XXV).
The liver glycerides contain considerable proportions of C 2 o-C 2 2
unsaturated acids with diminished proportions of palmitic acid. The
hoof oil of sheep resembles that of oxen, and the lowered content of
saturated acids is compensated for by high proportions of both palmitoleic and oleic acids. The hoof oil is the only fat in sheep with notable
proportions of palmitoleic acid.
Dahl considers that the changes in composition of horse fats from
the internal to external parts of the body are slight, and this view is
supported by the data shown in Table XXVI. However, in line with beef
brisket fat (see Table XXIV), horse wither fat was found by Dahl (318)
to contain somewhat higher (14.2%) proportions of palmitoleic acid.
The examples given for horse fats are taken from New Zealand
71
nephric and outer back fats results, in accordance with Hilditch's views,
from an exchange in the proportions of stearic and oleic acids.
In cattle, however, Dahl (318) considers that the differences between
the perinephric and external tissue fats arise from changes in the proportions of palmitoleic and stearic acid. This view is supported by the
analysis of an ox brisket fat, which shows about 17% palmitoleic acid as
compared with less than 2% normally present in the perinephric fat. It
is also supported to some extent by the work of Shorland and Hansen
(319) (see Table XXIV), though here the external tissue fat, as compared with the kidney fat, contains more oleic as well as palmitoleic acid
to compensate for the reduced proportions of stearic acid. In the New
Zealand sample of external tissue fat the stearic acid content is still
relatively high (13.4%) as compared with only 5.4% found by Dahl
(318). It is possible in the colder climates that the external tissue fats
are more unsaturated and contain less stearic acid. This accords with
the findings for pigs of Henriques and Hansen (322) where they show
that the iodine value is related to the temperature at the site of fat
deposition. It is conceivable that if the stearic acid content of the New
Zealand sample were lower the palmitoleic acid content would be
more in line with that found by Dahl (318).
The yellow marrow fat of the bone appears to correspond in its fatty
acid composition to that of other depot fats, whereas neatsfoot oil prepared from the hoofs of oxen is low both in stearic acid and palmitic
acid. Here the liquid nature of the fat is due to the high content of
both oleic and palmitoleic acids. In the liver glycerides the content of
palmitic acid is also low but is compensated for not by palmitoleic, but
by C 20 and C 22 highly unsaturated acids.
In the sheep the variations between the external tissue fats and
the perinephric fats, as in the pig, are largely the result of an exchange
between oleic and stearic acids (see Table XXV).
The liver glycerides contain considerable proportions of C 2 o-C 2 2
unsaturated acids with diminished proportions of palmitic acid. The
hoof oil of sheep resembles that of oxen, and the lowered content of
saturated acids is compensated for by high proportions of both palmitoleic and oleic acids. The hoof oil is the only fat in sheep with notable
proportions of palmitoleic acid.
Dahl considers that the changes in composition of horse fats from
the internal to external parts of the body are slight, and this view is
supported by the data shown in Table XXVI. However, in line with beef
brisket fat (see Table XXIV), horse wither fat was found by Dahl (318)
to contain somewhat higher (14.2%) proportions of palmitoleic acid.
The examples given for horse fats are taken from New Zealand