COELOM AND SEROUS  MEMBRANES) and the oblique vein of

Marshall . It can be readily reconstructed from figs . 4 and 5 if the transverse communication (L.I.) is obliterated . In some mammals the postcaval vein is double, especially, in its hinder (caudal) part, and this sometimes occurs as a human abnormality (see F . W . McClure, Am . Journ. of Anat. vol . 2, 1903, and vol . 5, 1906, also Anat . Anzeiger, Bd . 29, 1906) . Except in Cetacea, one or both azygos veins are always present in mammals .

When there is only one it is usually the right, though a few forms among the marsupials, rodents and ungulates have only the

left (F . E . Beddard, P.Z.S., 1907, p . 181) . In many of the lower mammals the external jugular vein is much larger than the internal and returns most of the blood from the brain through an opening called the postglenoid foramen . For• this reason it was formerly regarded as the representative of the primitive jugular . It. is now, however, thought that the internal jugular is that representative, and that the arrangement of man,. in which the internal jugular drains the interior of the cranium, is the more generalized and primitive . For further details and literature see R . Wiedersheim's Comparative Anatomy of Vertebrates, translated by W . N . Parker (London, 1907) . (F .

G .