OCR Text |
Show 1885.] VISCERAL ANATOMY OF BIRDS. 839 The dissection of two specimens of Bhea americana which have died during the course of the present year, enables m e to confirm the above-mentioned statements. In this bird, however, and in the Ostrich, the two cavities which contain respectively the right liver-lobe and the left liver-lobe, together with the gizzard, are floored by a tough membrane, which, behind the gizzard, becomes superficial, and covers over the coils of the intestine ; this membrane is attached laterally to the body-wall and to the " oblique" septa which form the inner boundaries of the posterior intermediate air-sacs. In the E m u (Dromaus) there is a close similarity to the condition met with in Struthio and Rhea. O n opening the bird by a median incision through the abdominal parietes, and reflecting the two cut halves of the musculature, the disposition of the viscera was seen to be practically identical with that of the other Struthiones. A tough membrane covers over the posterior section of the abdominal cavity ; just behind the gizzard this membrane is firmly attached to the oblique septum ; posteriorly it appears to be also attached to the oblique septum, but the two structures are in reality separable, and the horizontal membrane of the abdomen is continued upwards to the middle line of the body, where it is attached firmly in the neighbourhood of the spinal column. The right lobe of the liver, as in Struthio and Bhea, is enclosed in a separate pocket of peritoneum, and the left lobe appears to be contained within another cavity common to itself and to the gizzard; a more minute examination, however, has convinced m e that the gizzard is in reality enclosed in a distinct compartment, and is firmly attached to the parietes, as Prof. Huxley has stated of the gizzard of the Ostrich. Whether this is also the case with Bhea, I am unable to state. Mr. Parker has said nothing of the attachment of the gizzard to the parietes, and m y own notes upon the subject are unfortunately not sufficiently explicit. There is, as Prof. Huxley has shown, a close correspondence in many of these points with the structure of the Crocodile. In the Crocodile (Crocodilus acutus) (see fig. 1, p. 840) the viscera have the same relative position; the two lobesof the liver lie anteriorly, the gizzard is situated on the left side of the body behind the left lobe of the liver, while the intestines occupy the rest of the abdominal cavity. On opening the body-cavity the intestines are not visible ; they are in fact covered and concealed by a horizontal septum which runs from side to side of the body, this septum loosely covers the intestinal cells, it is not attached to them anywhere, but arises from the abdominal parietes ; anteriorly this membrane is firmly attached to the gizzard, and in fact divides into two layers which enclose aud completely shut off that viscus from the rest of the abdominal cavity. Tbe two lobes of the liver are likewise separated from each other and from the gizzard and the rest of the abdominal cavity by septa of fibrous tissue. The arrangement of tbe abdominal viscera in the Crocodile is therefore practically the same as that which I have just described in Dromaus; in both animals the intestinal coils are loosely covered by a horizontal membrane, and in both the two lobes |