Anafoviy of Notorycfes typhlops. 97 



normal coiiclitions present. The study of the blood vessels, with 

 the material at present obtainal)le, is not an easy matter, owing 

 partly to the very brittle and absolutely bleached, and often 

 quite transparent state of the vessels, and also to the great 

 quantity of adipose tissue surrounding them, with a considerable 

 admixture of strong fibres, which to the naked eye are often 

 much more like ordinary blood vessels than are those vessels 

 themselves. Recourse has frequently to be made therefore to 

 the compound microscope and staining fluids for certainty of 

 recognition. Especially is this so in the pectoral, abdominal, 

 and pelvic regions. The following details involve observations 

 made during a careful dissection of five individuals, aided by 

 microscopic sections of one or two parts, such as the limbs. 



77/*? Heart. 



The heart, which is normal in position, is somewhat more 

 pointed than is often the case, the apex being well directed 

 towards the left side, and separated dorsally from the diaphragm 

 by a small lobe of the right lung, as in marsupials generally, its 

 pericardium, however, being distinctly connected ventrally with 

 the diaphragm, a condition not usual in marsupials. So far as 

 can be seen there is no fossa ovalis on the auricular septum. In 

 the left ventricle the mitral valve has two well-marked papillary 

 muscles holding its chordae tendineae, one on the septum, the 

 other on the outer wall, while the right auriculo-ventricular 

 valve has three muscles corresponding to its three flaps. Tl>e 

 right ventricle takes no share in the formation of the apex. 



Pul»ionary Circulation. 



The main pulmonary artery is a short thick vessel arising from 

 the right ventricle, and leaving the heart externally just behind 

 the arch of the aorta. It divides almost immediately, and at a 

 point directly ventral to the trachea, and anterior to its division, 

 into the right and left pulmonary artery. The right branch is 

 somewhat shorter and wider than the left, each of the branches 

 lying ventral and somewhat anterior to the bronchus of its own 

 side. Each artery divides at its entrance to the root of the lung 

 into two main branches, the larger of which passes downwards 



