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CHARLES S. THORNTON
crowd into the area between the newly formed wound epithelium and the
cut ends of the stump tissues. These phagocytes are involved with
removal of detritus resulting from the degeneration of the injured ends of
the muscle and skeletal tissues (see Weiss and Rosenbaum, 1967). The
muscle fibers, for example, lose their striations in the region of injury
so that clear areas of sarcoplasm containing pycnotic and degenerating
nuclei are formed. Sarcolysis of the injured ends of the muscle fibers
continues and fragments of sarcoplasm with pycnotic nuclei separate
from the remaining, more proximal, muscle and these bits of detritus
become histolyzed and phagocytized (Thornton, 1938b).
The wound epidermis also plays a significant role in removal of detritus
during the phase of demolition. Many investigators have observed that
the wound epidermis becomes loaded with the products of tissue destruction (see extensive review by Singer and Salpeter, 1961). In the adult
newt, tongues of wound epithelium move down into the stump and engulf
scattered debris. In beryllium-poisoned limb stumps this epidermal
activity becomes greatly increased due to the great amount of tissue
destruction, and fragments within the epidermis range in size from
melanin granules to recognizable nuclear and cytoplasmic debris. Observations with the electron microscope (Singer and Salpeter, 1961) confirm
light microscope studies that debris in various stages of dissolution can
be seen within vacuoles of the epithelial cells. Indeed, Singer visualizes a
flow of materials, much of it dissolved in the intercellular fluid which is
present in excess amount in the demolition phase, from the stump into
the wound epithelium where some of it may be digested and utilized and
the remainder gradually moved to the surface and discharged.
The wound epithelium has also been reported to have histolytic functions in early phases of regeneration. Thus Taban (1955) observed the
liquefaction of a blood clot by the wound epithelium, and Adova and Feldt
(1939) reported proteolytic enzyme activity in wound epithelium of the
salamander. Therefore it is interesting to learn (Singer and Salpeter,
1961) that ultrastructural studies indicate that there is no basal membrane barrier between the lowest layer of epidermal cells, covering the
amputation surface, and the mesodermal cells of the limb stump. Furthermore, many cells of the wound epidermis possess a cisternal type of
endoplasmic reticulum, an ultrastructure which has consistently been
associated with cells engaged in the secretion of a protein-rich product.
Also, wound epidermal cells of the basal layer frequently have a broad
cortical zone which consists of a somewhat indistinct, uniform, spongy
material and contains no endoplasmic reticulum or mitochondria. Singer
CHARLES S. THORNTON
crowd into the area between the newly formed wound epithelium and the
cut ends of the stump tissues. These phagocytes are involved with
removal of detritus resulting from the degeneration of the injured ends of
the muscle and skeletal tissues (see Weiss and Rosenbaum, 1967). The
muscle fibers, for example, lose their striations in the region of injury
so that clear areas of sarcoplasm containing pycnotic and degenerating
nuclei are formed. Sarcolysis of the injured ends of the muscle fibers
continues and fragments of sarcoplasm with pycnotic nuclei separate
from the remaining, more proximal, muscle and these bits of detritus
become histolyzed and phagocytized (Thornton, 1938b).
The wound epidermis also plays a significant role in removal of detritus
during the phase of demolition. Many investigators have observed that
the wound epidermis becomes loaded with the products of tissue destruction (see extensive review by Singer and Salpeter, 1961). In the adult
newt, tongues of wound epithelium move down into the stump and engulf
scattered debris. In beryllium-poisoned limb stumps this epidermal
activity becomes greatly increased due to the great amount of tissue
destruction, and fragments within the epidermis range in size from
melanin granules to recognizable nuclear and cytoplasmic debris. Observations with the electron microscope (Singer and Salpeter, 1961) confirm
light microscope studies that debris in various stages of dissolution can
be seen within vacuoles of the epithelial cells. Indeed, Singer visualizes a
flow of materials, much of it dissolved in the intercellular fluid which is
present in excess amount in the demolition phase, from the stump into
the wound epithelium where some of it may be digested and utilized and
the remainder gradually moved to the surface and discharged.
The wound epithelium has also been reported to have histolytic functions in early phases of regeneration. Thus Taban (1955) observed the
liquefaction of a blood clot by the wound epithelium, and Adova and Feldt
(1939) reported proteolytic enzyme activity in wound epithelium of the
salamander. Therefore it is interesting to learn (Singer and Salpeter,
1961) that ultrastructural studies indicate that there is no basal membrane barrier between the lowest layer of epidermal cells, covering the
amputation surface, and the mesodermal cells of the limb stump. Furthermore, many cells of the wound epidermis possess a cisternal type of
endoplasmic reticulum, an ultrastructure which has consistently been
associated with cells engaged in the secretion of a protein-rich product.
Also, wound epidermal cells of the basal layer frequently have a broad
cortical zone which consists of a somewhat indistinct, uniform, spongy
material and contains no endoplasmic reticulum or mitochondria. Singer