MARSUPIALIA. 



305 



Fig. 130. 



Liver of the Koala. 



the convex surface of the liver. The coats of 

 the ductus choledochus are thickened towards 

 its termination, and become the seat of nu- 

 merous mucous cysts which open into the in- 

 terior of the duct. 



In thp Phalangers the terminal half-inch of 

 the ductus choledochus is similarly enlarged 

 and glandular. The biliary and pancreatic ducts 

 generally unite together before perforating the 

 duodenum. In the Virginian Opossum, the 

 long-nosed Bandicoot, and the long-tailed 

 Dasyure they pour their secretions into the gut 

 an inch from the pylorus. In the great Kan- 

 garoo the glandular ductus choledochus is 

 joined by the pancreatic duct, and terminates 

 in the duodenum five inches from the pylorus. 



The pancreas. The pancreas extends as 

 usual from the duodenum to the spleen, be- 

 hind the stomach ; it is characterized by a pro- 

 cess sent off at right angles, or nearly so, to 

 the main lobe at or near its left extremity. I 

 have observed other small and thin processes 

 branching out into the duodenal mesentery in 

 a Phalanger; and similar but still more nu- 

 merous processes, so as to give the organ a 

 dendritic appearance in the Kangaroo ; but the 

 first-named process is constant. 



The spleen. It is interesting to observe that 

 the spleen corresponds in this triangular or T- 



VO{.. III. 



shaped figure with the pancreas. In the great 

 Kangaroo ( Macropus major') I found the main 

 body of the spleen ten inches long, and the 

 rectangular process six inches ; both parts were 

 narrow and thin. 



Absorbents. The lacteal absorbents form, in 

 the Dasyurus viverrinus, two thin, subelongate, 

 dark-coloured mesenteric glands : one of these 

 is situated near the pylorus, at the end of the 

 pancreas. The plexiform cysterna chyli is si- 

 tuated in the Kangaroo ( Macropus Parry i was 

 the species from which the following descrip- 

 tion is taken) upon the crura of the diaphragm, 

 and extends upon the right side above the dia- 

 phragm into the thorax. Two thoracic ducts are 

 continued from the cysterna, one along the left, 

 the other along the right side of the bodies of 

 the dorsal vertebrae. The right duct crosses the 

 seventh vertebra and joins the left, which again 

 divides and reunites, forming a slight plexus, 

 before finally terminating at the confluence of 

 the left subclavian and jugular veins. The 

 double thoracic duct in the Kangaroo was first 

 noticed by Dr. Hodgkin ; it is interesting, on 

 account of its resemblance to the characteristic 

 condition of the great nutrient conduit in the 

 Bird and Crocodile ; in these, however, each 

 division terminates in the vena innominata of 

 its own side, which was not the case in the 

 Kangaroo above described. 



Blood. From the characteristic elliptical 

 form of the blood-discs of Birds and Reptiles, 

 and the rare occurrence of that form, as in the 

 exceptional case of the Camel tribe, among the 

 placental Mammalia, the examination of these 

 particles of the circulating fluid in the Marsu- 

 pial genera was attended with more than ordi- 

 nary interest, and the results, derived from a 

 comparison of species belonging to all the lead- 

 ing groups, show that the different tribes of 

 Marsupial animals correspond with the analo- 

 gous placental Mammalia both in the circular 

 or subcircular contour of the blood-discs, and 

 very nearly also in their size.* 



Dasyurus viverrinus. The blood-discs of 

 this small carnivorous Marsupial were sensibly 

 larger than those of the analogous placental 

 Mammalia, as the Cat. The ordinary or un- 

 broken disQ$ had tfaeir margin rounded off. 

 The number^f taes^rar.ulated discs was con- 

 siderable; many of "them presented a well- 

 defined margin, notched ii8* a-'fcog- wheel. The 

 average diameter obtained ^y ma was ^jjgth of 

 an inch. 



Dasyurus ursinus. The average diameter of 

 the blood-discs is ^ : observed extremes of 

 size ^ and ^ 



Perameles lagotis. The blood of this Mar- 

 supial, which was examined while recently 

 drawn from the living animal, and under the 

 same circumstances as that of the two species 

 of Dasi/urc, presented a still greater number of 

 the granulated blood-discs mixed with others 

 of the ordinary form. The descriptions of such 

 altered blood-discs not only by Hewson and 

 Falconer, and in recent times by Professor 



* See Medical Gazette, November 13, 1839, and 

 Mr. Gulliver's observations, London and Edinb. 

 Philos. Magazine, February, 1840. 



x 



