440 SGHULTE, SEI WHALE. 



lung is smooth and uniform showing no trace of fissures or of lobulation. The diaphragmatic 

 surface is separated from the mediastinal by a massive ridge, which fills the shallow pericardio- 

 diaphragmatic groove. On the costal surface, extending from apex to the projecting angle of 

 the caudal margin is a low sagittal ridge which divides this surface into dorsal and ventral por- 

 tions. It corresponds to the angles of the ribs. The foregoing, while applicable to both lungs, 

 is based more particularly upon the left; the right in consequence of the bend of the thorax 

 is somewhat flattened caudally and bears very deep impressions of the ribs on its costal surface. 

 The left lung has a length of 59 mm. Its greatest vertical breadth, at the pericardio-diaphrag- 

 matic angle is 22 mm.; its greatest thickness, at the same point, 16 mm. The right lung- 

 measures 55 mm. in length, 25 mm. in breadth, 14 in thickness; but these dimensions, especially 

 the last two, are altered by the deformation of the lung. The apices are blunt and are grooved 

 by the posterior thoracic artery and the accompanying vein, which cross them in a dorso-lateral 

 direction. The subclavian vessels in their arch over the first rib do not come in contact with 

 the apices of the lungs; the thoracic portion of the left artery is however in contact with the 

 mediastinal surface of the left lung. The interval between the subclavian arch and the apex 

 of the lung, must in my judgment be ascribed to a reduction of the lung itself, coincident with 

 and in excess of the skeletal shortening affecting the cervical and upper thoracic regions. 



Mliller l in the course of an elaborate study of the lungs of aquatic mammals has described 

 those of Balcenoptera musculus. A comparison with his figures shows a general close resemblance 

 to the conditions present in this fcetus, but in his specimen the apex is more deeply grooved. 

 His seventeenth figure shows a left lung dorso-ventrally flattened, the right having a well 

 marked ridge, which probably corresponds to the angles of the ribs, in contrast to the flattened 

 right lung and more smoothly rounded ridge on the costal surface of the left lung in this fcetus. 

 Evidently the question of preservation and in particular the position of the foetus in its contain- 

 ing jar is a factor, which ought not to be lost sight of in considerations upon the form and surface 

 relief of the viscera. 



The mediastinal surface is separated from the diaphragmatic by a well defined ridge which 

 is in apposition with the fat pad of the pericardio-diaphragmatic junction. Both surfaces are 

 concave, the mediastinal strongly so when it comes to be applied to the pericardium ventral to 

 the hilum. Rostrad it becomes convex, on the left side presenting a gutter for the termination 

 of the aortic arch, from which ascends towards the apex a shallow subclavian groove. On the 

 right side in this surface is a deep notch-like groove extending to the apex, which lodges the 

 tracheal bronchus. The depth of the groove seems to have been exaggerated and its angu- 

 larity occasioned by the torsion of the fcetus to the right. The point of entry of the bronchus 

 is 4 mm. from the apex. The hilum of the left lung has a length of 15 mm. Its upper extremity 

 is 17 mm. from the apex and 7 mm. from the ventral margin, its lower 11 mm. from this margin. 

 On the right side the entrance of the tracheal bronchus is independent of the hilum, with which 

 it is connected only by a continuous pleural reflection. Between the two ventrally and the 

 shallow groove of the precava is a prominence of the mediastinal surface. The main hilum has 

 a length of 18 mm. and its rostral end is 12 mm. from the apex. 



Pericardium. The pericardium is broadly exposed between the ventral margins of the 

 lungs and is separated from the thoracic wall only by the sinus costomediastinales of the pleurse. 



1 Milller, O. Untersuchungen iiber die Veranderungen welche die Respirationsorgane der Saugetiere durch die Anpassung an das 

 Leben in Wasser erlitten haben. Jena. Zeitschr. f. Naturw., Bd. 32. 1898. 



