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Abstract

The arterial main root enters into the otic capsule as a branch of the a. auditiva interna with the n. octavus (n. acusticus) (Luedicke, 1964, 1978). The venous main root is situated close to it, in the vicinity of the acoustic nerve. Sometimes, through the blackening effect of the Scribtol injection, it is very hard do distinguish these two vessels, especially if they are surrounding the nerve or if they are lying on top of each other obstructing the view. These difficulties do not occur in differentiating the vessels of the human ear. As Siebenmann (1894), to whom most modern authors refer in their anatomic work, has pointed out that the little trunks and main branches of the arteries are either coiled or corkscrew like. Unfortunately, this is not the case for most of the serpents examined thus far. It was only by lucky coincidence that a primitive serpent like Eryx conicus, a boid, was shown to have the same characteristics that are found in the vessels of the human membranous labyrinth. Because the arterial main root in the various families of the Serpentes generally supplies the same areas, there does not seem to be any difficulty later on in distinguishing the veins from the arteries, if they are not twisted. The eye of the observer can be trained to recognize a very weak meandering of the arterial flow as it has been found, for example, in Natrix (see also Luedicke, 1978, Fig. 10 a.Z.). One should not be deceived by shrinking processes that can occur after demineralization or after the fading of pigmentation by chlorodioxide in nitric acid. The determination of the type of vessel was confirmed by white-gelatine injection (Kobold, 1964) and by histologic analysis.