DIAPHRAGM— DICTUM 135 



sense (and that is uncertain) he used the word. Dr. Sharpe {Cat. 

 B. Br. Mm. x. pp. 3, 54 et seqq.) refers it to the Dkxidx — a group 

 which, he says, "cannot be defined in exact ierm^ " {iom. cif. 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 Pardalotm antedates DlC^EUM, and, according to usage, 

 the Family is called after the oldest genus it contains. 



DIAPHRAGM (Greek 8Lu.c{)pay[xa), 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 diflerently arranged, consisting 

 (1) of the pulmonary or transverse, and (2) of the abdominal or 

 oblique jDortion. 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 aponeurotic membrane, Avhile it is 

 connected with the vertebral column as the median vertical septum ; 

 completely sej>arating 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 

 again either half into four loculi, into each of which one of the three 

 or four post-bronchial AiR-SACS extends from the lungs. Con- 

 sequently the whole of the diaphragmatic memljranes 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. 



DIC.EUM, a group differentiated by Cuvier in 1817 (B^gne 

 Aniiii. i. p. 410) for the Certhia cruentata of Linnaeus 

 and its allies, several of which inhabit India, and 

 one of them — D. Jiirundinaceum — Australia, in Avhich 

 country the scientific name has been accepted as dicbum. 



English (Gould, Hcmdb. B. Austral, i. p. 581). The (After Swainson.) 

 group has since been recognized as entitled not only to generic rank. 



