LANDRY, S..O.; State University of New York, Binghamton: Venous Drainage in Short- and Long-faced Mammals

In mammals, the venous drainage of the head proceeds through two major channels. The veins of the rostrum unite to form the facial vein, which picking up the linguo-facial and the superficial temporal vein, becomes the external jugular vein. (Humans are an exception.). The venous drainage of the brain case, proceeds from the uniting of the various veins of the brain (especially the superior and inferior sagittal sinuses) to form the transverse sinus at the occipital end of the brain case. This sinus, runs laterally and exits the cranial cavity as the internal jugular vein, after picking up the superior petrosal sinus, which runs backward along the lateral wall of the brain case. Between the two drainage systems is the ophthalmic plexus which can drain blood in either direction. In mammals with large rostra, the greater drainage volume should be via the external jugular, and the jugular foramen should be relatively small, while in short faced forms the greater volume should be via the internal jugular, and the foramen relatively larger. Comparison of series of Dog and Cat skulls shows this supposition to be correct. The length of the foramen/width of skull divided by the rostral length/total length of skull gives a double proportion that is significantly larger in cats. Non parametric statistics must be used for the comparison.