With the mandible at rest, electromyographic recordings were obtained from the anterior temporal, lateral pterygoid, and digastric muscles with the subjects (A) sitting upright with the head unsupported, (B) inclining backwards with the back-rest at an angle of 45", and (C) supine. Two minutes after a shift in posture the electrical activity in the anterior temporal muscles was strongest in the upright position, it decreased slightly when the back-rest was at 45", and was least in the supine position. The digastric muscles showed a pattern similar to that of the temporal. The activity in the lateral pterygoid muscles was strongest when the subject was inclined backwards at 45". The influence, therefore, of these muscles on the posterior border position of the mandible varies with posture. In all the muscles studied there was least activity when the subject was in the supine position. This would suggest that the supine position is suitable .for recording the most retruded position of the mandible. In the intermediate position the lateral pterygoid muscles appear to counteract retrusion.Quantitated Plectromyographic recordings from the 'muscles of mastication of subjects seated upright, with the head unsupported, and the mandible at rest have shown slight, but distinct activity (Moller 1966). T'he present study deals with the postural activity in the temporal, lateral pterygoid, and digastric muscles, i. e. muscles determining the vertical and horizontal position of the mandible. With the subjects sitting upright, inclined backwards, and in the supine position, the aim was to locate the posture in which the mandible was least influenced by muscle activity. It was the assumption that in such a posture registration of the most retruded position of the mandible would be facilitated. This question was not considered in the previous electromyographic studies of head posture concerning either the action of the postcervical muscles (Halbert 1958) or the change in the position of the mandible with the head tilted forwards and backwards (Vanoucek 1957, Preiskel 1965).In the supine position the load of the mandible is directed towards the temporomandibular joints. Recordings, therefore, in this position might indicate whether or not retrusion of the mandible is influenced by the action of the lateral pterygoid muscles (Aprile 8 Saizar 1947.

Dental pulps from 45 caries-free primary or permanent teeth and from 24 carious primary teeth were investigated for presence of mast cells (MC) . All the pulps were removed from split teeth and fixed in Newcomer's fluid or lead acetate-formalin. Serial sections stained with hematoxylin-eosin, astra blue (pH 0.2-0.3) + nuclear fast red, and toluidine blue (pH 1.0) demonstrated that pulps without inflammatory cells or with a few small lymphocytes were devoid of typical MC, even in the strongly metachromatic regions. However, MC were noted in all inflamed pulps; the number, distribution, and appearance of the MC depending upon the severity and type of the inflammatory reaction.

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