In order to control the size of marking spot in cerebral cortex, a new electrolytic method was improved and the rectangular current (1 Hz, 0.5sec. duration) was supplied by a constant current isolator. This technique indicates that the polarizing effect occured at the tip of tungsten microelectrode was much less than the ordinary method. Inserting the microelectrodes into the cortices, the electrolytic lesions were made by the several current flows in vivo. The relationship between the spot size (μm²) measured histologically and quantity of electricily (coulomb) supplied through the electrode was determined systematically. Within some current range, the marking spots varied proportionally in diameter with increase in quantity of electricity and the range of optimum quantity was 12×10^-6 to 15×10^-6 coulomb. After the single neuron which responded to the tooth pulp stimulation was detected electro-physiologically, the rectangular current of 12×10^-6 coulomb was supplied to make a micro-lesion for histological identification.

Then the location of the neuron was pursued microscopically and the spot dyed by Nissl method showed that the identified neuron was located at the deep layer of lamina III in the middle part of anterior suprasylvian gyrus.

The molar tooth gerom from the mandibules of newborn rabbits were examined by scanning electron microscopy. At the cervical margin, the enemel surface was characterized by numerous deep pits (honeycomb pattern) caused by the Tomes’ processes of the ameloblasts. To wards the top of the cusps the pits gradually smoothed out and these impressions were occupied by the cuboidal reduced enamel epithelium.

The cuboidal reduced enamel epithelia were barely attached on the enamel surface by their fine cytoplasmic projections.

At the top of the cusps, the enamel matrix was coated directly with the sheet-like fibrous structure. The surface of ameloblasts were covered over with the collagenous network structure origipated from the stratum intermedium.

A typical case of nasoalveolar cyst has been reported.

A 47-year-old woman was referred to our clinic, complaining of swelling in the region of the left nasal vestibulum of about six years’ duration.

Physical examination revealed a swelling of the size of the small finger-tip. The semitransparent and viscid fluid was aspirated by exploratory puncture.

Posteroanterior and lateral view of the x-ray film of the skull with radiopaque medium showed a well-defined extent of cyst within the soft tissues.

Under local anesthesia with 2% lidocaine, the cyst was enucleated.

The postoperative course was satisfactory.

Histopathologic diagnosis was nasoalveolar cyst.