Considerations on the morphogenesis of target and targetoid fibres based on morphometric investigations.

A man of 68, who died from a second heart stroke had neurogenic atrophy of the legs. The anterior tibial muscle showed abundant target and targetoid fibres. Half a year prior to death he had increasing weakness and wasting of the legs. The morphometric evaluation of the target and targetoid fibres showed a considerable independence of the plane size of the single zones from the total gauge of the fibres on cross section. Only a small part of the variation in size of zone 2 (4%) depended on the size of the target, indicating that zone 2 cannot just be a passive product of a shrinkage and disappearance of the target, but that there must be an active process, which leads to the change in zone 2. The regressive development of the centrally demarcated fibrillar bundle (target) is regarded as secondary degeneration following interruption of the nutritional supply.