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The radiological features of seven cases of pelvic digit discovered incidentally on plain radiographs are described and differentiation from other causes of new bone formation is discussed. Its recognition as a benign anomaly is important to avoid unnecessary investigation or intervention. An embryological theory of development of pelvic digit is proposed.

The development of cutaneous innervation in the rat and the mouse has been studied by silver techniques. In particular, the innervation patterns of adult and of perinatal skin have been compared. From the second prenatal day until the sixth postnatal day, the relatively thick epidermis is freely penetrated by nerve fibers; thereafter, the nerve endings appear to be confined to the dermis. The intraepidermal axans are directed obliquely, with a rough (and not exact) correspondence to the plane of future emergence of the hair shafts. The appearance of a transitory intra-epidermal innervation in rodent hairy skin is interpreted in the light of the development of intra-epidermal nerves elsewhere.In the perinatal period the surface epithelium of mouse and rat skin undergoes a pronounced but transient architectural change. The germinal cells which lie beneath the fetal periderm multiply some five days before birth to form a deeply stratified epidermis with basal, spinous, granular and horny elements. Within two weeks after birth the epidermis assumes its adult form by reversion to a double layer of cells, thinly covered by keratin (Glucksmann, '45; Butcher, '51; Slee, '62). This paper reports and discusses the associated changes in epidermal innervation. MATERIAL AND METHODSForty-two albino mice of BALB or Schneider strains, and 40 Wistar rats, were used. Thirty mice were sacrificed between the sixteenth day of gestation and the eleventh postnatal day, inclusively, to show the daily development of cutaneous innervation. Thirty-two rats provided daily material for the same period. The remaining 20 animals supplied adult skin for comparison.Following an overdose of chloroform, skin pieces from the mid-dorsal trunk of all the younger animals were mounted flat on filter paper to prevent curling, and fixed in alcoholic Bouin's solution. The older skin did not retract and the pieces were fixed without mounting. The nerves were studied i n serial 15 CI paraffin sections after staining with a double-impregnation protargol method (FitzGerald, '64). In addi-J. COMP. NEUR., 126: 37-42.

We reviewed the clinical and radiological features of ten patients with small arteriovenous malformations that caused intracerebral hematomas. In six patients, angiography showed a small nidus (less than 1 cm in diameter) with a shunt at the site of the hematoma, and in four only an early-filling vein was evident. Six patients had only delayed angiography (4 weeks or more after the ictus). In three, angiography within 2 days of the ictus failed to reveal the cause of the bleed, but repeat angiography showed an early-filling vein in two, and a nidus with shunting in one. In only one patient did early angiography reveal the malformation. MRI was obtained in eight patients, and in two prominent vessels were evident in the wall of the hematoma cavity. In investigation of an unexplained intracerebral hematoma, MRI may be useful to exclude a neoplasm or cavernoma, although the latter may be not be evident in the presence of a recent hematoma. We suggest early MRI and angiography for investigation of an unexplained, nonhypertensive intracerebral bleed, with follow-up MRI and delayed angiography if the initial studies fail to reveal the cause.

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The innervation of the skin of hairless mice has been studied following induction of epidermal hyperplasia by physical and chemical methods. Physical stimuli comprised ultraviolet irradiation, heat, wounding, and friction. Effective chemicals included benzene, carbon tetrachloride, chloroform, creosote, formaldehyde, hexadecane, hydrobromic acid, sodium lauryl sulfate, and turpentine. Epidermal hyperplasia, however produced, was associated with growth of sensory nerve fibers into the outer part of the epidermis. Following a single 10-min exposure to an ultraviolet sunalmp at 40 cm, the nerves extended into the epidermis within 24 hr and disappeared during the second week as the epidermis reverted to its normal thickness. Repeated irradiation (until tumors appeared) was accompanied by persistent hyperplasia and neural invasion. Of 32 papillomas examined, intraepithelial nerves were found in 28. The presence and location of nerves in the tumor epithelium were related to the incorporation of tactile hair disc epithelium. The hyperplastic regenerative epithelium at the margins of skin ulcers were also invaded by nerves which sometimes followed the migrating epithelium across the ulcer floor. Since the regenerative epithelium was not directly treated, it was concluded that the proliferation of nervous tissue in response to skin injury was the result of the hyperplasia per se, regardless of the method used to produce it.

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