1889.J THE BODY-CAVITY IN LIZARDS, ETC. 461 



Figs. 8, 9, and 10 show this right-hand sac at the beginning of the 

 9th day, and we see (fig. 10, y. TF.) that the foramen of Winslow is 

 still open. But on the 9th day this foramen becomes closed (that 

 is, I could find no aperture in a complete series of sections of a chick 

 of 9 days 1 hour incubation), and moreover that part of the recess 

 which surrounds the gizzard, as opposed to the oesophagus, becomes 

 obliterated' (compare fig. 12, 2, with fig. 10, 2), 



This space (2), which can be followed through the sections of the 

 12th day (cf. figs. 14-17 and 26-28) and seen in those of the adult 

 fowl (figs. 44-46), corresponds, as stated, to rather more than the 

 "recessus superior sacci omenti" of Mammals, since its posterior 

 part represents a portion of the omental sac. For this reason, 

 and because there is a similar space on the left side (where there is 

 no omental sac to have a recess), and because these spaces are in fact 

 no mere diverticula of the omental sac, but have a distinct origin, I 

 have spoken of them as the pulmohepatic recesses (cf. ante, p. 454). 

 This name expresses their relation to the liver and respiratory 

 organs, and to the pulmohepatic ligaments which form part of their 

 outer wall. 



In the fowl the foramen of "Winslow up to the 9th day, when it 

 closes, has precisely the same relations as in Mammals, being 

 bounded by the inferior vena cava antero-dorsally, and the duodeno- 

 hepatic omentum, or ventral mesentery that bears the bile-ducts 

 and portal vein, postero-ventrally. 



With regard to the corresponding recess on the left side (2' in 

 the figures previously referred to), a reference to the figures shows 

 that it is from the first in much freer communication with the rest 

 of the peritoneal cavity than that on the right, and the alimentary 

 canal, instead of (as in the case of the other recess) bending round 

 to form, together with the median vertical membrane that supports 

 it ipi, figs. 9, 12, 14, 15), a posterior or omental wall, appears 

 rather on the contrary to hinder the development of its outer wall 

 by leaning over on the left side between the lung and liver. 



III. (d). On the Homology of the Avian and Mammalian 

 Diaphragms. 



On considering the relations of the recesses and ligaments (2, 2', 

 a, a) in the two above-named groups, we see that the whole of the 

 Mammalian diaphragm lies laterally or centri.^ugally to the attach- 

 ments (a, a) of the liver to the mediastinal tissues in front of it, while 

 the avian diaphragm lies practically entirely within or centripetally 

 to these attachments. So that the condition in birds is expressed by 

 saying that the middle mediastinal tissue of the two sides, instead of 

 coming to wrap round the pericardium, diverges posteriorly and 

 ventrally to become attached to the lateral body-walls^. 



'^ Apparently by constriction off from the rest and the adhesion of its walls. 



^ We may, for iUustratiou, compare the middle mediastinal tissue of birds in 

 its relation to the pericardium to a coat which, instead of being buttoned 

 across the chest (the pericardium), is extended like a wing on either side by 

 laying hold of the front bottom corners. 



