310 



MARSUPIALIA. 



three-sided, one side convex, the second con- 

 cave and applied to the pericardium, the third 

 side concave, and in contact with the dia- 

 phragm. 



In the Potoroo the left lung is unilobate with 

 a fissure on the anterior or upper edge; the 

 right lung has two or three deep fissures. The 

 azygos lobe is elongated, pointed, and triedral, 

 as in the Kangaroo. 



In the Petaurists and Phalangers the right 

 lung is trilobate, the left bilobate ; there is also 

 a lobulus azygos. The Koala has the lungs 

 similarly divided, and not simple as in the 

 Wombat. 



In the Opossums, Dasyures, and Perameles 

 the right lung is usually trilobate, (bilobate in 

 Didelphys brachyuru,) and with the usual 

 azygos appendage : the left lung is commonly 

 divided into two, but is sometimes entire, as in 

 the Perameles and Didelp/i. bntchyura. In all 

 the Marsupials the right lung is the largest, 

 owing to the oblique inclination of the heart to 

 the left side. 



The thyroid glands are two disunited bodies 

 in the Dasyures ; they were each the size of a 

 horse-bean in the Das. macrurus. They were 

 of the same size in a Phalangista J'uliginosa, 

 but were united by a filamentary strip passing 

 between their lower extremity, across the first 

 tracheal ring. In the Koala, the thyroid gland 

 is situated lower down extending from the 

 fourth to the ninth or tenth tracheal ring. In 

 the Wombat I found the thyroid glands two 

 elongated bodies of a dark colour reaching 

 from the thyroid cartilage to the seventh tracheal 

 ring on each side. 



The larynx of the Marsupialia consists of a 

 cricoid, thyroid, and arytenoid cartilages and 

 an epiglottis. The latter is always remarkable 

 for its large size, and generally for its emar- 

 ginate apex. There is no muscle passing from 

 the epiglottis to the tongue; its base is con- 

 nected in the Kangaroo by a triangular fascia 

 to the body of the os hyoides and the greater 

 cornua; and a small muscle passes from the 

 middle part of the body of the os hyoides to 

 the dorsum linguae. 



In the Phalangers the epiglottis is broad 

 and short, and with a bifid apex. In the Pe- 

 rameles and Phascogale the sides of tlie broad 

 and short epiglottis are attached to the apices 

 of the arytenoid cartilages, retaining thus much 

 of its early condition, which will be adverted to 

 in the account of the peculiarities of the mam- 

 mary fetus. 



In the Perameles lagotis I found on the base 

 of the tongue in front of the epiglottis a 

 small saccukis of mucous membrane, which 

 communicated by a regular symmetrical cre- 

 scentic aperture, situated between the body of 

 the os hyoides and the thyroid cartilage, and 

 continued down in front of the thyroid cartilage : 

 the surface of the cavity was smooth and lubri- 

 cated, and it seemed to be for the purpose of 

 facilitating a hinge-like motion between the 

 thyroid cartilage and the body of the os hy- 

 oides. 



The thyroid cartilage is convex externally and 

 protuberant in the Phalangers and Koala, but 



offers no particular modification in other Mar- 

 supials. The base of the arytenoid cartilages 

 is broad in the antero-posterior direction, and 

 the chordae vocales short and feebly developed. 

 The Marsupials have little or no voice : the 

 Wombat emits a guttural hissing sound : the 

 Dasyurus ursinus a snarling growl or whine : 

 the Thylacine is described as uttering a short 

 guttural cry. I have never heard a vocal note 

 of any kind from the Kangaroos, Potoroos, Pe- 

 taurists, Phalangers, or Perameles. 



Renal system. The kidneys present a simple 

 conglobate external form in all the Marsupials, 

 as \njig. 134, o, o, and in their structure and po- 

 sition in the abdomen agree with the Mamma- 

 lian type of structure. 



In the Macropus Purryi the kidneys are 

 situated six inches above the brim of the 

 pelvis, and lying in the same transverse line: 

 they have the same relative position in other 

 Poephaga. 



In the Koala the right kidney is higher by 

 its whole length than the left. In the Dasy- 

 uri macrurus and viverrinus, the right kidney 

 lies half an inch higher or in advance of the 

 left : in this carnivorous genus a few branches 

 of the renal veins are distributed upon the sur- 

 face of the kidney, but not in the same pro- 

 portion or with the beautiful arborescent dis- 

 position characteristic of the kidneys of the 

 Cats, Suricates, and Hyaena. In a Dasyurus 

 mucrurus weighing three pounds eight ounces, 

 the two kidneys weighed thirteen drachms. 

 In a Phalangista vulpina, weighing five pounds 

 three ounces, the two kidneys weighed only 

 ten drachms. 



The substance of the kidney is divided into 

 a cortical and medullary part ; the former is 

 generally a thin layer. The tubuli uriniferi 

 terminate on a single mammilla which projects 

 into the commencement of the ureter in the 

 Opossums, but does not extend beyond the 

 pelvis of the kidney in the Kangaroos. In 

 the Kangaroos the medullary substance forms 

 several lateral abutments to the base of the 

 main mammilla. 



The supra-renal glands generally present the 

 relative position and proportions to the kidneys 

 represented in the Kangaroo, at fig. 134, p. 

 They are, as in most of the smaller quadrupeds, 

 less flat than in man : the right body generally 

 adheres to the coats of the vena cava, and the 

 left to the renal vein. In the Dasyures the ex- 

 ternal stratum is light-coloured ; this surrounds 

 a dark-coloured layer, and then there is a light- 

 coloured central part, but no cavity. 



The ureters terminate at the buck of the neck 

 of a muscular and pendulous urinary bladder 

 (t), which only exhibits a trace of u radius at 

 the middle of its anterior part in the young 

 marsupial, while in the maternal pouch. 



Male organs of generation. The testes, 

 which are still abdominal at the time of birth, 

 descend, soon after the foetus is transferred to 

 the pouch, into the external pedunculate pre- 

 penial scrotum ; the canal of communica- 

 tion between the abdominal cavity and the tu- 

 nica vaginalis is long and narrow, but always 

 remains pervious. 



