1898.] 



SYSTKM OF THE CHITfOPTEKA. 



65 



Thymus \ 



The general collection of tissue that has in the aggregate been 

 called the thymus gland is developed to an unusual extent in the 

 Chiroptera. In this species it is composed of gland-like masses 

 irregular in outline, showing a tendency to separate into smaller 

 lobules. This tissue is scattered about the middle mediastinum, one 

 mass being placed at the base of the heart, another ventral to the 

 pericardium where it meets the diaphragm, another within the 

 pericardial sac, at the base of the great vessels. The relation of the 

 gland to the pleura is very intimate. 



The Heart. 



Of large size even for the Chiroptera, measuring 26 X 15 x 15 mm. 

 The general shape is that of an elongated oval, placed very obliquely 



Fig. 3. 



Heart of Pteropus edulis, ventral surface, X li-— I. 1-4. Intercostal arteries 

 in the iipner foiir spaces of the right side, 1 and 2 arising from the 

 Vertebral,'.^ and 4 from the Innominate. I.M.V. Internal Mammary 

 Veins, joining the Right and Left Precaval yeins. V.A.M. Vena azygos 

 major. 



' The description applies to the naked-eye appearance of this structure. 

 Microscopic sections (specimen A) show numerous much vacuolated cells, with 

 no definite arrangement, intimately related to blood-capillaries, and with no 

 ducts. Sections of the same gland in specimens and D show only adipose 

 tissue. Fui-ther investigation is necessary to reconcile the appearances 

 observed. 



Peoc. Zool. Soc— 1898, No. V. 5 



