nce of the
bitter of the hop itself. So closely does the hop bitter resemble that
of quassia, that in seasons of hop failure it is said to be employed
as a substitute in brewing, and at one time its use for that purpose
was prohibited by law.

As a further proof that the bitter principle of the hop is distasteful
to the aphis, it is noticeable that when the fly first arrives it
always attacks the topmost shoots of the bine where the leaves have
not developed, and where the active principle is likely to be weakest.
The same position is selected by the aphis of the rose, the bean, and
every plant or tree subject to aphis attack--it is the undeveloped and
therefore unprotected part which is chosen.

It is remarkable that when a destructive blight is
proceeding--generally in a wet and cold time--and a sudden change
occurs to really hot dry weather, the hop plant often recovers its
tone automatically, shakes off the disease, and the blight dies away,
a fact which strengthens the assumption that in normal weather the
plant can protect itself. Again, the blight is always most persistent
under the shade of trees or tall hedges, or where the bine is over
luxuriant, when owing to the exclusion of light and air the plant is
unable to elaborate its natural safeguard.

Fertilizers not well balanced as to their constituents, and containing
an excess of nitrogen, act as stimulants without supplying the
minerals necessary for perfect health. The effect is the same as that
produced in man by an excess of alcohol and a deficiency of nourishing
food, the health of the subject suffers in both cases, leaving a
predisposition to disease.

Reasoning by analogy, these causes affecting the success or failure of
plants give us the clue to the remedies for bacterial disease in man.
Disease is the consequence and penalty of life under unnatural or
unfavourable conditions, which should first receive attention and
improvement. When in spite of improved conditions disease persists,
specifics must be sought. The conditions which produce disease in the
vegetable world are fought by the active principle of each plant, and
inasmuch as the germ diseases of man are probably, though distantly,
related to those which affect vegetable life, the specific protections
of plants should be exploited for the treatment of human complaints.
This, of course, has for long been a practice, but possibly more
success might be achieved by careful research to identify