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PHYSIOLOGICAL CONSIDERATION OF CELLS. 525
of the parent into two equal parts, each of which when detached absorbs
nutrient matter, and, soon attaining the same size as the mother-cell,
multiplies in turn. The principle enunciated by Virchow twenty years
ago, Omnk cdlula e celluld, is as much in force now as then. Discov-
eries regarding the methods of cell-multiplication have been made, but
no instance of metaplasia between members of different groups or fam-
ilies has been demonstrated. That the repair of tissues depends upon
the multiplication of cells of like families is the accepted belief of his-
tologists to-day. A surface denuded of its epithelium does not recover
itself from the connective tissue beneath, but from the edges of the
wound by tlie extension of the borders toward the centre, thus gradu-
ally forming a complete skin. It is true that the regeneration of con-
nective tissue is through granulation-tissue, but granulation-tissue is
developed from the escaped white blood-cells ; and I think we can
place white blood-cells in the list of connective tissues developed from
the mesoblast. The change from white blood-cells to plasma-cells and
fixed connective-tissue cells is simply a matter of adaptation to environ-
ment.
We come now to the consideration of the third attribute of cells
that of functional activity. The life of the individual rests in the life
The human body is made
of the individual elements that compose it.
up of millions of individualities which are dependent upon a special
localized principle for their functional activity. These units of life not
only have the power of individual cellular activity, but, united, they
form organs which are but the expressions of their aggregation. A
tissue is what it is by reason of the elements that constitute it, and the
function it performs is only the united expression of its component
parts. Cellular activity, then, is the basal principle that underlies all
visible life-functions.
The limit of duration as regards the life of an organism is in adverse
ratio to the scale it occupies in the order of being. A perversion of
physiological action in the individual organism gives rise to a patho-
logical condition known as disease. Total and permanent cessation of
functional activity is that state of being which we recognize as death.
Death may result from outside influences or by reason of the cells hav-
ing performed their life-office.
Cells are developed to perform well-known physiological actions,
and when a pathological result is produced it has its origin in some
outside influence. Cells have not the power to produce pathological
results unless stimulated by some agent which lies without the bounds
of physiological action ; and when so stimulated they act through their
original channels. Thus, we see that pathological conditions are only
perverted physiological conditions. Many physiological processes pre-
sent pathological ajjpearances, but when we study their deeper expres-
sions we find that they are purely physiological. For instance: in the
development of bone, giant-cells or osteoclasts are always present taking
down the first-formed' bone from the inner side, while the osteoblasts
are adding to its circumference. In the resorption of the roots of tem-
porary teeth we find another excellent example of physiological action
which bears upon its face the stamp of a pathological process. In this
PHYSIOLOGICAL CONSIDERATION OF CELLS. 525
of the parent into two equal parts, each of which when detached absorbs
nutrient matter, and, soon attaining the same size as the mother-cell,
multiplies in turn. The principle enunciated by Virchow twenty years
ago, Omnk cdlula e celluld, is as much in force now as then. Discov-
eries regarding the methods of cell-multiplication have been made, but
no instance of metaplasia between members of different groups or fam-
ilies has been demonstrated. That the repair of tissues depends upon
the multiplication of cells of like families is the accepted belief of his-
tologists to-day. A surface denuded of its epithelium does not recover
itself from the connective tissue beneath, but from the edges of the
wound by tlie extension of the borders toward the centre, thus gradu-
ally forming a complete skin. It is true that the regeneration of con-
nective tissue is through granulation-tissue, but granulation-tissue is
developed from the escaped white blood-cells ; and I think we can
place white blood-cells in the list of connective tissues developed from
the mesoblast. The change from white blood-cells to plasma-cells and
fixed connective-tissue cells is simply a matter of adaptation to environ-
ment.
We come now to the consideration of the third attribute of cells
that of functional activity. The life of the individual rests in the life
The human body is made
of the individual elements that compose it.
up of millions of individualities which are dependent upon a special
localized principle for their functional activity. These units of life not
only have the power of individual cellular activity, but, united, they
form organs which are but the expressions of their aggregation. A
tissue is what it is by reason of the elements that constitute it, and the
function it performs is only the united expression of its component
parts. Cellular activity, then, is the basal principle that underlies all
visible life-functions.
The limit of duration as regards the life of an organism is in adverse
ratio to the scale it occupies in the order of being. A perversion of
physiological action in the individual organism gives rise to a patho-
logical condition known as disease. Total and permanent cessation of
functional activity is that state of being which we recognize as death.
Death may result from outside influences or by reason of the cells hav-
ing performed their life-office.
Cells are developed to perform well-known physiological actions,
and when a pathological result is produced it has its origin in some
outside influence. Cells have not the power to produce pathological
results unless stimulated by some agent which lies without the bounds
of physiological action ; and when so stimulated they act through their
original channels. Thus, we see that pathological conditions are only
perverted physiological conditions. Many physiological processes pre-
sent pathological ajjpearances, but when we study their deeper expres-
sions we find that they are purely physiological. For instance: in the
development of bone, giant-cells or osteoclasts are always present taking
down the first-formed' bone from the inner side, while the osteoblasts
are adding to its circumference. In the resorption of the roots of tem-
porary teeth we find another excellent example of physiological action
which bears upon its face the stamp of a pathological process. In this
