[Parameters of digitally averaged potentials of individual motor units]

Of sixty normal subjects of different age six different muscles each were examined electromyographically. The activity pattern was recorded for moderate voluntary innervation and superposed digitally. The parameters of digitally averaged summation action potentials were compared with those of manually assessed potentials. The two methods gave identical results: The duration of potentials was between 5 and 10 ms. It increased in the younger and older age groups and showed only slight changes in middle-aged persons. Only minor differences were found between the muscles of one age group, an exception being the orbicularis oris muscle. The results obtained are compared with values reported in the literature.

[Congenital aplastic anemia, type I]

Case report of a 7 year old girl, anaemic since birth. The anaemia, of variable intensity, is associated with a moderate reticulocytosis. Bone marrow films, show a marked erythroblastosis with conspicuous morphological abnormalities and internuclear chromatin bridges. The erythrocinetic pattern is that of ineffective erythropoiesis. The morphologic features are those of Heimpel and Wendt's type I congenital dyserythropoiesis. The erythrocytes are lysed by some acidified sera, thus showing a membrane anomaly which is unusual in type I. However the characteristics of the lysis are different from those of type II (HEMPAS) erythrocytes.

EVIDENCE ON THE SIMPLE STRUCTURE AND FACTOR INVARIANCE ACHIEVED BY FIVE ROTATIONAL METHODS ON FOUR TYPES OF DATA

Five methods of factor rotation-Maxplane, Oblimax, Promax, Harris- Kaiser, and Varimax-were applied to four types of data-questionnaire, objeckive test, a physical problem, and a plasmode. In addition, the Maxplane procedure was followed in each case by Rotoplot-assisted visual robations. The results were compared with respect to simple structure (hyperplane percentages) and factor invaniance (congruence coefficient). It was concluded that, in general, the oblique methods were superior to Varimax in terms of simple structure although not consistently in terms of factor invariance. Among the oblique methods, the Rotoplot-assisted Maxplane usually resulted in the maximum simple structure at the f .10 hyperplane width but not consistently at either of the other two arbitrarily chosen widths. The unassisted Maxplane was generally excelled by the less expensive oblique methods both wiith respect to hyperplane count and factor invariance. The Harris-Kaiser method was generally more satisfadory in terms of the two criteria combined.