| OCR Text |
Show 640 MR. W. F. R. WELDON ON THE [Dec. 1 8, the rest are hidden by a thick horizontal septum of connective tissue stretching across the whole body-cavity from the pericardium to the cloaca. The attachments of this septum are, anteriorly, to the posterior margin of the pericardium ; laterally, to the side walls of the abdomen, just ventral to the line of attachment of the oblique septum; and posteriorly, to the body-wall just ventral to the anus. The liver is, as has been said, entirely ventral to this septum, while the stomach perforates it. The umbilical ligament is converted into a strong vertical septum, running between the lobes of the liver, and extending anteriorly to the pericardium, posteriorly to the middle of the gizzard (fig. 6, v. sepi). This arrangement of septa is found in all the Storks I have dissected l, and is exactly repeated in Phoenicopterus, while I have not found it in any other birds. In all the Anatidae, for example, the representative of the horizontal septum is attached to the ventral abdominal wall, almost immediately behind the liver, so that it does not cover any of the intestinal coils2. The arrangement above described is associated, both in Phoenicopterus and the Storks, with a peculiarity in the air-cells themselves. The pulmonary aponeurosis3 is not muscular. The prabronchial air-cells vary greatly in size, and are divided by a complicated arrangement of transverse septa into smaller chambers ; in Leptoptilus there are five such chambers in each cell, in Phoenicopterus four. This divided condition is not dependent on the size of the cells, because in Phoenicopterus, where they are small and deeply buried among the muscles of the neck, the dividing septa are as well developed as in the Adjutant, where each air-cell extends nearly a third of the way up the neck. The subbronchial cells are completely fused, no trace of the original partition remaining. The fused cells project forwards between the clavicles, from which a small horizontal septum projects, partially dividing a prseclavicular from a postclavicular portion. The praeclavicular portion is compressed by a muscle, which radiates over its outer surface from the clavicle. The anterior and posterior intermediate cells present nothing remarkable, their relations being sufficiently shown. Indeed the condition of these cells seems, so far as I have been able to ascertain, to be singularly constant in all birds. The abdominal cells are very large, extending to the extreme end of the body. The oblique septum, in the abdominal region, is attached to the vertebrae very near the middle line ; passing ventral-wards, the two septa diverge, forming a chamber in which lie the 1 Leptoptilus argala and javanicus ; Ciconia nigra and C.maguari; Mycteria americana ; Tantalus sp. ? ; Carphibis spinicollts; Xenorhynchus senegalensis. 2 This septum has been mentioned by various authors ; but, so far as I am aware, no special name has been applied to it. From its resemblance to a modified Mammalian mesentery, I would propose to call it "pseudepiploon." 3 For an explanation of the terms used in describing air-cells, see Huxley, " On the Respiratory Organs of Apteryx," P. Z. S. 1882, p. 560 et seq. |
