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CA L CIFICA TION. 73

Calcification.
Calcification is a process by which organic tissues become hardened
by a deposition of salts of calcium within their substance. In the intercel-
hilar tissue and in the substance of the cells themselves, these salts are
deposited by the rich blood supply always near. They are deposited in
minute particles and in such fine subdivisions as to make it difficult
to, demonstrate many of them even with the higher powers of the mi-
croscope. The intercellular substance, either a protoplasmic or gelati-
nous fluid or semifluid, contains the calcium particles. In it they change
their nature chemically, uniting \vith the albuminous organic substance
of the part, and form small globular bodies which have been called
calco-spherites ; and these, blending or coalescing at the point of cal-
cification, form a substance called calco-globulin. This calco-globulin,
wliich is a lifeless matter, has been deposited through the cells into the
gelatinous substance, where, by a further hardening process, it becomes
the fully calcified matrix.
Mr. Rainey, and later Prof. Harting and Dr. Ord, have devoted
much time to the study of this substance. Mr. Rainey found that if
a soluble salt of calcium be slowly mixed Avith another solution capable
of precipitating it, the resultant calcium salt will go down as an amor-
phous powder, and sometimes as minute crystals. But when the cal-
cium salts are precipitated in gelatin, the character of the calcium salts
is materially altered. Instead of a powder, there were found various
curious, but definite, forms quite unlike the crystals or powder produced
without the intervention of the organic substance. Mr. Rainey found
that if calcium carbonate be slowly formed in a thick solution of albu-
min, the resultant salt has changed in character ; it is now in the form
of globules, laminated, like tiny onions, which coalesce into a laminated
mass. In this Mr. Rainey claims to find the clue for the explanation
of the development of shells, teeth, and bone.
At a more recent date. Prof. Harting took up this line of investiga-
tion and found that other calcium salts would behave in a similar man-
ner. The most important addition to our knowledge made by Prof.
Harting lay in the very peculiar constitution of the " calco-spherite,"
by which name he designated the minute globular forms seen and
described by Rainey. Mr. Rainey found that albumin actually en-
tered into the composition of the globule, since it retained its form
even after the action of acids. Prof. Harting has shown that the
albumin left behind after treatment of a calco-spherite with acid is
no longer ordinary albumin ; it is profoundly modified, becoming
exceedingly resistant to the action of acids. For this modified albu-
min he proposes the name " calco-globulin." Microscopic glistening