[Gross and light microscopic observations of the pudendal nerve of the guinea pig (author's transl)].

Using thirty six adult guinea pigs, the course and distribution of the pudendal nerve was observed macroscopically and then the constitution of the myelinated nerve fibers in these branches was studied with the fan-wise split preparation method (Fukuyama) and the cross sections embeded in paraffin wax. The main findings are summarized as follows: 1) The pudendal plexus in the guinea pig is formed most frequently by a bigeminal nerve which arises from the ventral ramus of the second sacral nerve at an average rate of 55.0% and the pudendal nerve is so independent from the sciatic nerve that the most part of the bigeminal nerve runs into the pudendal nerve. 2) The perineal nerve of the guinea pig arises most frequently with four roots (43.3%). The myelinated fiber constitution of this nerve is as follows: The small-sized fibers occupy 49.8%, the medium--sized 21.9%, the large--sized 15.1%, the maximum--sized 13.1% on an average, and the nerve fiber diameters observed in the cross section shows a bimodality in their distribution, of which the fibers in the higher peak are 1 mu to 2 mu and in the lower peak 5 mu to 8 mu. 3) The dorsal nerve of the penis or clitoris of the guinea pig arises most frequently with one root from the originating roots of the perineal nerve. The relationship between the sciatic and dorsal nerve appears to be scanty. The myelinated fibers of this nerve comprise 50.8% of small--sized, 28.4% of medium--sized, 14.7% of large--sized and 6.2% of maximum--sized fibers on an average. The fiber sized histograms constructed in the cross section shows a unimodality laying at 1 mu to 3 mu and the dorsal nerve of the clitoris contains more medium fibers 3 mu to 6 mu than the perineal nerve. From these results, it seems clear that the genital corpuscles are supplied by these medium fibers. 4) The inferior rectal nerve of the guinea pig arises from the perineal nerve in all cases, however, it is very slender. 5) The branch to the Obturator internus arises from the originating root or main trunck of the perineal nerve (51.7%). The myelinated fiber constitution of this branch is as follows: The maximum--sized fibers occupy 67.6%, the large--sized 16.2%, the small--sized 9.5% and the medium sized 6.8%. On the other hand, the fiber diameters observed in the transverse section are distributed around three peaks lying at 1 mu, 8 mu to 9 mu and 12 mu to 13 mu. 6) The branch to the accessory head of the Semitendinosus arises from the pudendal nerve at an average rate of 91.7%, of which this branch arises most frequently with one root from the originating root of the perineal nerve. The myelinated fiber constitution is as follows: The maximum--sized fibers 50.0%, the large--sized 23.9%, the small--sized 15.9% and the medium--sized 10.2% on an average. The histogram shows that myelinated fibers in this muscular branch consist of two groups of 1 mu to 2 mu and 12 mu to 14 mu...