parts not previously containing it. In the course
of a disorder proceeding favourably, these humours undergo spontaneous
changes in quality. This process is spoken of as _coction_, and is the
sign of returning health, as preparing the way for the expulsion of the
morbid matters--a state described as the _crisis_. These crises have a
tendency to occur at certain periods, which are hence called _critical
days_. As the critical days answer to the periods of the process of
coction, they are to be watched with anxiety, and the actual condition
of the patient at these times is to be compared with the state which it
was expected he ought to show. From these observations the physician may
predict the course which the remainder of the disease will probably
take, and derive suggestions as to the practice to be followed in order
to assist Nature in her operations.

Hippocrates thus appears to have studied "the natural history of
diseases." As stated above, his practice was to watch the manner in
which the humours were undergoing their fermenting coction, the
phenomena displayed in the critical days, and the aspect and nature of
the critical discharges--not to attempt to check the process going on,
but simply to assist the natural operation. His principles and practice
were based on the theory of the existence of a restoring essence (or
{physis}) penetrating through all creation; the agent which is
constantly striving to preserve all things in their natural state, and
to restore them when they are preternaturally deranged. In the
management of this _vis medicatrix naturae_ the art of the physician
consisted. Attention, therefore, to regimen and diet was the principal
remedy Hippocrates employed; nevertheless he did not hesitate, when he
considered that occasion required, to administer such a powerful drug as
hellebore in large doses.

The writings which are extant under the name of Hippocrates cannot all
be ascribed to him. Many were doubtless written by his family, his
descendants, or his pupils. Others are productions of the Alexandrian
school, some of these being considered by critics as wilful forgeries,
the high prices paid by the Ptolemies for books of reputation probably
having acted as inducements to such fraud. The following works have
generally been admitted as genuine:--

1. On Airs, Waters, and Places.
2. On Ancient Medicine.
3. On the Prognostics.
4. On the Treatment in Acute Diseases.
5.