DIAPHRAGM—DICAUM 135 
sense (and that is uncertain) he used the word. Dr. Sharpe (Cat. 
BL. Br. Mus. x. pp. 3, 54 et seqg.) refers it to the Dicwide—a group 
which, he says, “‘cannot be defined in exact terms” (fom. cit. p. 2), 
and the genus Pardalotus is made to consist of 9 species. If this 
assignment be correct, the name of the Family should be changed, 
as the genus Pardalotus antedates Dicmum, and, according to usage, 
the Family is called after the oldest genus it contains. 
DIAPHRAGM (Greek duddpaypa), the transverse muscular 
partition below the heart and lungs and above the liver, stomach, 
and rest of the intestinal canal, fully developed in Mammals only. 
In Birds it is incomplete and rather differently arranged, consisting 
(1) of the pulmonary or transverse, and (2) of the abdominal or 
oblique portion. The first arises from the second to the sixth 
pairs of ribs near the lateral edge of the lungs, and spreads over 
their ventral surface as an aponeurotie membrane, while it is 
connected with the vertebral column as the median vertical septum ; 
completely separating the lungs and the cervical air-sacs from the 
rest of the thoraco-abdominal cavity. Small voluntary muscles 
arising from the ribs and from the sternum extend over part of the 
aponeurosis. The second or oblique half is entirely membranous 
without muscular fibres: it forms the continuation of the ventral 
margin of the vertical median septum, and is connected with the 
pericardium and with the medio-ventral portion of the sternum, 
while the rest extends obliquely through the abdominal cavity to 
the posterior and ventral margins of the sternum. The space thus 
enclosed is the subpulmonary chamber, divided into a right and a 
left half by the vertical septum. Three transverse septa divide 
ie either half into four loculi, into each of which one of the three 
> four post-bronchial AtR-SAcS extends from the lungs. Con- 
ay the whole of the diaphragmatic membranes divide the 
entire thoraco-abdominal cavity into three chambers: (1) the 
Pulmonary chamber, anteriorly and dorsally from the pulmonary 
septum, containing the lungs and cervical air-sacs; (2) the Sub- 
pulmonary chamber, anteriorly and ventrally from the oblique 
septum, and ventrally from the pulmonary septum, containing 
most of the air-sacs; and (3) the Cardio-abdominal chamber, 
posteriorly from or below the oblique septum, containing the heart 
and the rest of the intestines. 
DICAUM, a group differentiated by Cuvier in 1817 (fegne 
Anim. i. p. 410) for the Certhia cruentata of Linnzeus 
and its allies, several of which inhabit India, and 
one of them—D. hirundinaceum—Australia, in which fe 
country the scientific name has been accepted as Diceum. 
English (Gould, Mandpe Bb. Auciral, i.0p: 081). >be: CAter Syainsqus) 
group has since been lane as entitled not only to generic rank, 
