Cunningham begins his summary on the structure of the internal organs with comments on the pericardium and its specific attachments before proceeding to discuss the external appearance and internal structure of the heart.  He notes that the thylacine's heart is narrow, elongated and pointed with a very capacious right auricle and its appendix, whilst showing no indication of bifurcation is peculiar on account of its great breadth.  Cunningham then discusses his observations on the internal structure of the chambers of the heart and concludes by noting two distinguishing features of the marsupial heart:

    1. The absence of all traces of an annulus ovalis and fossa ovalis.
    2. The peculiar position of the right auricle of the orifices of the great cardiac vein.
 

    Cunningham then proceeds to make observational comments on the trachea and lungs.  He notes that the length of the trachea in the specimen he is dissecting is 17 cm (6¾ in.) and is comprised of 34 cartilaginous rings, which are deficient superiorly throughout its entire length.  He observes that the left lung is undivided by any marked fissure with a deeply crenated margin and that the right lung is divided into three lobes and rests by its base upon the upper surface of the diaphragm.

    Cunningham then turns his attention to the examination of the abdominal viscera and writes that the stomach of the thylacine has a close resemblance in appearance to that of man.  The curvatures however are more pronounced and the transition from the wide cardiac portion of the stomach to the narrow pyloric part more sudden with the fundus rising high above the cardiac opening.  Cunningham provides detailed measurements of the stomach obtained from the female specimen and then proceeds to discuss its internal structure.
 

. Alimentary tract of the thylacine - measurements taken from Cunningham (1882).

He states that the intestinal canal of the thylacine is remarkably short and shows no differentiation into large and small intestine.  The calibre of the intestinal canal is to a great degree uniform throughout its entire length.  Cunningham notes the length of the canal for the male specimen as 195.58 cm (6 ft. 5 in.), and the female specimen as 142.24 cm (4 ft. 8 in.).  In the anterior part of the tube the villi of the intestinal wall are filamentous in shape and about 1.27 cm (½ in.) long.  They are arranged sparsely over the mucous surface giving it a rough, shaggy appearance.  As one progresses down the intestine the appearance of the villi change as they gradually become stouter and more club-shaped and finally stunted and conical before disappearing some 40.5 cm (16 in.) before the anal opening.