Common Rat. 3 



that limb, is seen passing- up to join another vein, which, from its 

 being" placed superficially to the sterno mastoid muscle, we know to 

 be the homolog-ue of the external jugular of anthropotomy. The ex- 

 ternal jug-ular is the main trunk by which the blood from the interior 

 of the skull returns to the heart in the Rodents and many of the 

 lower Mammalia, and by its confluence with the vein from the 

 anterior limb the vena cava descendens is constituted. Internally 

 to the external jug-ular, just above its confluence with the subclavian 

 vein, is seen a part of the hibernating ° gland; externally to it 

 lies the submaxillary ; above this again we see the parotid with its 

 duct ; and above the parotid, the facial portion of the lacrymal g-land 

 sending- up a duct, under which a piece of blue paper is placed, to 

 enter the orbit and join there with the duct of a second portion 

 of the lacrymal gland, which is placed within the orbit, and an- 

 teriorly to the duct of the extraorbitaljj-placed portion. Within 

 the orbit we see the Harderian gland. For a fuller description of 

 these glands, see Description of Plate I, which represents a dis- 

 section somewhat different from that which we have of these 

 organs in this preparation. 



In the middle line of the body inferiorly to the heart we see the 

 cut surfaces of the six sternal bones, and in the angle intercepted 

 between the lowermost of these and the diaphragm, we see some 

 lobules of fatty tissue set in the process of serous membrane which 

 connects the apex of the pericardium with the sternal bones and 

 with the diaphragm. From these structures a vein passes back 

 along the pericardium to end in the vena cava descendens of the 

 left side. 



In the angle between the inferior surface of the diaphragm and 

 the lumbar muscles, the two psoas muscles and the quadratus 

 lumborum of the left side, we see the smooth-surfaced kidney, 

 which by this external character, as also by the internal one, of 

 the separation of its cortical or secretory from its medullary or 

 excretory parts, characterizes the class Mammalia. The spleen is 

 in relation with it on the right ; to the right of the spleen we have 

 the left end of the stomach, which is less vascular and glandular 

 than the pyloric half, which is here concealed and overlapped by the 



« For the histology and literature of the Hibernating Gland, see Hirzel and Frey in 

 Siebold's and Kolliker's ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xii. Hft. ii. 

 1862. 



