A reexamination of rat ductuli efferentes

In 33 testes from a random selection of rats a 10% suspension of India ink in normal saline was introduced through the rete testis into the emergent ductuli efferentes. Low-power microscopy and microradiography confirmed the individually independent origin of each ductule. Five ductules were isolated in each of 17 testes, 4 ductules in 6, 6 ductules in 8, and in 2 testes, 7 and 9 ductules, respectively. In six animals minor variations existed as between the right and left testes +/- 1 in 4 and +/- 2 in 2. It is necessary to exercise great caution in the interpretation of results of experimental work on alteration of the ductuli, because of variability between colonies and within strains of rats.