under unfavorable conditions for healing, cannot recover from the injury
rapidly or satisfactorily.

[Illustration: FIG. 59.--A large inflammatory growth following an injury to
the front of the hock.]

WOUND HEALING.--The following forms of healing commonly occur in wounds:
First and second intention; under a scab, and by abnormal granulation.

_Healing by first intention_ occurs when the wound is clean cut and there
is very little destruction of tissue, and when there is no suppuration or
pus formation. The blood and wound secretions cause the edges of the wound
to adhere. After a few days or a week the union becomes firm. Very little
scar tissue is necessary in this form of healing.

_Healing by second intention_ is characterized by pus formation and
granulation tissue. After the first day, the surface of the wound may be
more or less covered by red, granular-like tissue. Later this granular
appearance is modified by an accumulation of creamy pus and swelling of the
part, and finally scab formation and contraction of the new scar tissue.

Abrasions and superficial wounds usually _heal under a scab_. The scab is
formed by the blood and wound secretions. This protects the surface of the
wound until finally the destroyed tissue is replaced by the granulations,
and the skin surface is restored.

_Abnormal granulation_ is not an uncommon form of healing in domestic
animals. Mechanical and bacterial irritation causes the injured tissue to
become swollen and inflamed. In such a wound, excessive and rapid
granulation occurs, the new tissue piling up over the cut surfaces and