Architecture of the mesonephric nephron in pig and rabbit.

As a precondition for determining nephron profiles in sections, mature mesonephric nephrons from pig and rabbit embryos were isolated by a maceration technique in order to demonstrate nephron architecture, length, and diameter. In the pig the proximal tubule is largely constant. In the distal tubule the pre-attachment zone shows the greatest variation. The zone of attachment ot the corpuscle and the ventrolaterally directed post-attachment coil has a predictable course as does the collecting tubule. In contrast to earlier reports, the nephron shows no drastic differences in tubule diameter and is up to 33 mm long. The proportional length of the three major nephron segments is surprisingly constant. The rabbit nephron, although much shorter (4 mm) and simpler, with an alomst S-shaped pattern, is less easily understood in sections. Marked irregularities in its course are caused by the different behaviour of the terminal proximal segments. The distal tubule shows an ampullary dilatation in the attachment zone but can be very narrow in the pre-attachment part.