Using serial sections of 0.5 μ thickness from the renal cortex of a perfused and fixed rat glomerulus 2 models (scale 1:1650) were constructed to study glomerular vessel distribution. In the first model the routes of the capillaries were reconstructed as wax plates and a model of the complete glomerulus was built up. On the basis of this model a second was constructed in which wire was used to demonstrate the capillary distribution. Our findings were as follows: 1. The rat glomerulus consists of 5 lobularlike structures which receive their blood supply from one or two capillaries arising from the vas afferens. 2. After leaving the vas afferens the capillaries divide dichotomously. They may converge again and subsequently reunite to form a network that may take on a lobular appearance. 3. Multiple connections exist between the lobularlike structures. These anastomic connections pass through the centre of the glomerulus. It is mainly due to these connections that the lobular structure of the capillary convolution, as seen in the peripheral glomerular areas, does not continue to the hilar region. Because of this peculiarity the glomerular capillary convolutions have a lobularlike appearance. A direct connection between the vas afferens and the vas efferens could not be demonstrated. 4. Studies on the efferent drainage revealed that not every lobule and its own capillaries drained into the corresponding vas efferens, but that they occasionally drained into neighbouring vasa efferentia. 5. The volume of the glomerulus was 0.000706 mm3, the surface area was 0.236464 mm2, and the total length of the capillaries 8.705 mm. © 1979 Springer-Verlag.
