104
WERNER BERGMANN
By the middle of the nineteenth century cholesterol had been isolated from animal tissues and secretions, from bile fluid and blood,
from egg yolk and brain, and by the end of the century its ubiquity in
animals had been generally recognized. In gallstones and in brain tissues
cholesterol is present in the free state almost exclusively. In other places
it occurs mainly as fatty acid esters. Thus 73% of the cholesterol of blood
serum, 0.15-0.25 gm. per 100 ml., is present in the esterified form (3).
After cholesterol had been isolated from animal sources too numerous
to mention here, the belief took hold that it was indeed the universal
sterol of the animal world. Even in a most recent monograph reference
is made in the preface to "the universal distribution of cholesterol in all
animal tissues." If it were true indeed that cholesterol is the principal
sterol of all animals, there would be but little justification for the writing
of a chapter which is to deal with the comparative biochemical aspects
of sterols. Fortunately, however, there exists a significant diversity among
the principal sterols of animals. This became apparent during the first
decade of the present century with the discovery that in certain animals
cholesterol is replaced totally or in part by closely related compounds.
New sterols had been obtained from a sponge (4) and from insects (5).
Doree (6) was the first to point to the possible significance of variations
among animal sterols. His study was one of the first comparative biochemical studies, and it merits the designation of a classic in its field.
The object of his investigations was clearly outlined in the opening paragraph of his report: "If cholesterol is a body which is one of the
primary constituents of animal protoplasm, we should expect to find it
not only in the highly organized animals, but throughout the series
from Chordata to Protozoa, or if cholesterol were not present, its place
should be filled by other and closely related forms. In the latter case
it might be found that each of the great classes of the animal kingdom
was characterized by the presence of a different member of the cholesterol family. On the other hand, if cholesterol is not of primary importance to all forms of life, it is not impossible that animals might be
found in the composition of whose protoplasm it did not enter."
Doree isolated and characterized the sterols from one or two representatives of the larger phyla of the animal kingdom. Since he found
sterols in the animals under investigation he inferred their presence in
all animals. He obtained cholesterol not only from warm-blooded
animals, but also from other vertebrates and from invertebrates including such primitive forms as sea anemones. While he did not find a
sterol typical for each phylum, Doree showed that in at least two invertebrates, a sponge and the common starfish, cholesterol is replaced
by another related substance. His studies were paralleled at about the
WERNER BERGMANN
By the middle of the nineteenth century cholesterol had been isolated from animal tissues and secretions, from bile fluid and blood,
from egg yolk and brain, and by the end of the century its ubiquity in
animals had been generally recognized. In gallstones and in brain tissues
cholesterol is present in the free state almost exclusively. In other places
it occurs mainly as fatty acid esters. Thus 73% of the cholesterol of blood
serum, 0.15-0.25 gm. per 100 ml., is present in the esterified form (3).
After cholesterol had been isolated from animal sources too numerous
to mention here, the belief took hold that it was indeed the universal
sterol of the animal world. Even in a most recent monograph reference
is made in the preface to "the universal distribution of cholesterol in all
animal tissues." If it were true indeed that cholesterol is the principal
sterol of all animals, there would be but little justification for the writing
of a chapter which is to deal with the comparative biochemical aspects
of sterols. Fortunately, however, there exists a significant diversity among
the principal sterols of animals. This became apparent during the first
decade of the present century with the discovery that in certain animals
cholesterol is replaced totally or in part by closely related compounds.
New sterols had been obtained from a sponge (4) and from insects (5).
Doree (6) was the first to point to the possible significance of variations
among animal sterols. His study was one of the first comparative biochemical studies, and it merits the designation of a classic in its field.
The object of his investigations was clearly outlined in the opening paragraph of his report: "If cholesterol is a body which is one of the
primary constituents of animal protoplasm, we should expect to find it
not only in the highly organized animals, but throughout the series
from Chordata to Protozoa, or if cholesterol were not present, its place
should be filled by other and closely related forms. In the latter case
it might be found that each of the great classes of the animal kingdom
was characterized by the presence of a different member of the cholesterol family. On the other hand, if cholesterol is not of primary importance to all forms of life, it is not impossible that animals might be
found in the composition of whose protoplasm it did not enter."
Doree isolated and characterized the sterols from one or two representatives of the larger phyla of the animal kingdom. Since he found
sterols in the animals under investigation he inferred their presence in
all animals. He obtained cholesterol not only from warm-blooded
animals, but also from other vertebrates and from invertebrates including such primitive forms as sea anemones. While he did not find a
sterol typical for each phylum, Doree showed that in at least two invertebrates, a sponge and the common starfish, cholesterol is replaced
by another related substance. His studies were paralleled at about the