d hornblende which at first is rather fibrous
and tends to spread outwards through the surrounding felspar. Chlorite
also is abundant both in sheared and unsheared diabases, and with it
calcite may make its appearance, or the lime set free from the augite
may combine with the titanium of the iron oxide and with silica to
form incrustations or borders of sphene around the original crystals
of ilmenite. Epidote is another secondary lime-bearing mineral which
results from the decomposition of the soda lime felspars and the
pyroxenes. Many diabases, especially those of the teschenite
sub-group, are filled with zeolites.

Diabases are exceedingly abundant among the older rocks of all parts
of the globe. Popular names for them are "whinstone," "greenstone,"
"toadstone" and "trap." They form excellent road-mending stones and
are much quarried for this purpose, being tough, durable and resistant
to wear, so long as they are not extremely decomposed. Many of them
are to be preferred to the fresher dolerites as being less brittle.
The quality of the Cornish greenstones appears to have been distinctly
improved by a smaller amount of recrystallization where they have been
heated by contact with intrusive masses of granite. (J. S. F.)

DIABETES (from Gr. [Greek: dia], through, and [Greek: bainein], to
pass), a constitutional disease characterized by a habitually excessive
discharge of urine. Two forms of this complaint are described, viz.
Diabetes Mellitus, or Glycosuria, where the urine is not only increased
in quantity, but persistently contains a greater or less amount of
sugar, and Diabetes Insipidus, or Polyuria, where the urine is simply
increased in quantity, and contains no abnormal ingredient. This latter,
however, must be distinguished from the polyuria due to chronic granular
kidney, lardaceous disease of the kidney, and also occurring in certain
cases of hysteria.

_Diabetes mellitus_ is the disease to which the term is most commonly
applied, and is by far the more serious and important ailment. It is one
of the diseases due to altered metabolism (see METABOLIC DISEASES). It
is markedly hereditary, much more prevalent in towns and especially
modern city life than in more primitive rustic communities, and most
common among the Jews. The excessive use of sugar as a food is usually
considered one cause of the disease, and obesity is supposed to favour
its occurrence, but many observer