veloped, but
any gross loss of muscular tissue is replaced by a fibrous cicatrix. It
would appear that portions of muscle transplanted from animals to fill
up gaps in human muscle are similarly replaced by fibrous tissue. When a
muscle is paralysed from loss of its nerve supply and undergoes complete
degeneration, it is not capable of being regenerated, even should the
integrity of the nerve be restored, and so its function is permanently
lost.

_Secretory Glands._--The regeneration of secretory glands is usually
incomplete, cicatricial tissue taking the place of the glandular
substance which has been destroyed. In wounds of the liver, for example,
the gap is filled by fibrous tissue, but towards the periphery of the
wound the liver cells proliferate and a certain amount of regeneration
takes place. In the kidney also, repair mainly takes place by
cicatricial tissue, and although a few collecting tubules may be
reformed, no regeneration of secreting tissue takes place. After the
operation of decapsulation of the kidney a new capsule is formed, and
during the process young blood vessels permeate the superficial parts
of the kidney and temporarily increase its blood supply, but in the
consolidation of the new fibrous tissue these vessels are ultimately
obliterated. This does not prove that the operation is useless, as the
temporary improvement of the circulation in the kidney may serve to tide
the patient over a critical period of renal insufficiency.

_Stomach and Intestine._--Provided the peritoneal surfaces are
accurately apposed, wounds of the stomach and intestine heal with great
rapidity. Within a few hours the peritoneal surfaces are glued together
by a thin layer of fibrin and leucocytes, which is speedily organised
and replaced by fibrous tissue. Fibrous tissue takes the place of the
muscular elements, which are not regenerated. The mucous lining is
restored by ingrowth from the margins, and there is evidence that some
of the secreting glands may be reproduced.

Hollow viscera, like the oesophagus and urinary bladder, in so far
as they are not covered by peritoneum, heal less rapidly.

_Nerve Tissues._--There is no trustworthy evidence that regeneration of
the tissues of the brain or spinal cord in man ever takes place. Any
loss of substance is replaced by cicatricial tissue.

The repair of _Bone_, _Blood Vessels_, and _Peripheral Nerves_ is more
conveniently considered in the chapters dealing with these str