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Neuromuscular biopsies were taken from palmaris longus in 5 healthy young male volunteers. Measurements were made of muscle fibre cross-sectional area, of synaptic area and of the terminal innervation ratio. Marked differences in mean cross-sectional area of the muscle fibres, extending from 2832 to 4854 μ 2 were observed which could not be correlated with either the height and weight of the subject, or with their customary physical activity. Mean values for synaptic area extended from 177.4 to 224.9 μ 2, and there was a proportionality between this figure and the mean cross-sectional area of the muscle fibres. Statistical analysis of the frequency distribution curve for muscle fibre cross-sectional area and synaptic area established that they correspond to a normal or a logarithmic-normal distribution. There is no indication of a heterogeneity of muscle fibres and of end-plate populations, as far as their dimensions are concerned. Collateral branching occurs in 7.3-18.4% of the motor axons and more than one bifurcation along these fibres is exceptional. The pooled terminal innervation ratio of 1.12 1 is very near to the value previously considered to be normal. © 1970., SCOPUS: ar.j, info:eu-repo/semantics/published

The functional, or true terminal innervation ratio (TIR) was estimated on 13 neuromuscular biopsies taken from 5 palmaris longus and 7 tibialis anterior muscles in 7 male and 6 female healthy young volunteers. Axonal ramification resulting in the innervation of more than 1 muscle fibre by 1 subterminal axon occurs in 10.6% of the total number of axons studied. Most of the branching axons (94%) innervate 2 muscle fibres. Only 5.1 of them supply 3 muscle fibres by trifurcation. Innervation of 4 muscle fibres by 1 ramified subterminal axon is extremely rare and was observed in 0.9% of branching fibres, i.e. in 0.1% of all axons studied. There is no significant difference between the TIR of palmaris longus and that of tibialis anterior, nor between the values obtained in males and females. A mean TIR of 1.12 was obtained (range 1.05-1.20). Statistical analysis indicates that values higher than 1.25 are outside the normal range of distribution. © 1973., SCOPUS: ar.j, info:eu-repo/semantics/published