226 MB. r. E. BEDDAttD ON ME [Feb. 4, 



called ' diaphragm ' (' diaphragme thoraco-abdominal,' Sappey ; 

 ' diaphragmite thoraco-abdominal,' Milne-Edwards) is a more 

 or less aponeurotic fibrous membrane, continuous with the 

 ventral edge of the median dorsal septum and suspended by it, 

 like the roof of a tent, across the thoraco-abdominal cavity. In 

 the middle line, this oblique septum slopes downward and forward 

 to the dorsal and anterior face of the pericardium, with which its 

 fibres become firmly connected on their way to their attachment 

 to the sternum. fVora the median line, the two halves of the 

 oblique septum slope laterally and ventrally until they attach 

 themselves to the parietes of the abdomen behind, to those of the 

 thorax more anteriorly, and to the margins of the sternum in 

 front." 



In fact, if we make a transverse section through a Duck or most 

 other birds at the level of about the middle of the sternum, the 

 appearances will be such as are diagrammatically represented in 

 the accompanying drawing (fig. 1, p. 227). Pour membranes are 

 there visible — the intestines being left out of consideration for the 

 purposes of simplification, and as not germane to the structures 

 at present under discussion. The first of these is the falciform 

 ligament, which divides the lobes of the liver and is attached below 

 to the middle line of the sternum. Then there are the oblique 

 septum (O.S.), attached below to the sternum laterally, and above 

 to the parietes ; and finally the horizontal septum (A.S.), which 

 floors the two cavities containing the liver-lobes. 



This arrangement, however, does not hold good for a number of 

 Passerine birds; and it is possible — though I am not yet in a 

 position to make a definite statement about the matter — that the 

 arrangement which I am about to describe as characteristic of 

 many Passerines will be found to be distinctive of the group. 

 I commence with a somewhat detailed description of the oblique 

 septa of a Crow ( Gorvus capellanus) (see fig. 2, p. 227). As I have 

 dissected three examples of this bird, the following description 

 will probably be found to be free from any record of abnormal 

 conditions. 



The right lobe of the liver is considerably larger than the left, 

 and extends some way beyond the margin of the sternum, in fact 

 about as far as to the end of the postei-ior intermediate air-sac. It 

 is separated from the liver-lobe of the left side as usual by a 

 vertically directed septum, the umbilical or falciform ligament ; 

 this falciform ligament is attached to the ventral parietes for a 

 distance of about an inch — from the posterior end of the sternum 

 to a point rather in front of that which corresponds to the 

 posterior margin of the liver. Anterior to the posterior edge of the 

 sternum, the falciform ligament is not attached to that bone ; it 

 becomes fused ivith the two oblique septa, forming a roof over the liver- 

 lobes in this region, which is separated by a wide interval from the 

 internal surface of the sternum. 



The oblique septa are closely attached for a considerable distance 

 to the Hver-lobes, the adhesion being certainly not pathological. 



