THE SYSTEMATIC ANATOMY OF A FCETAL SEA-LEOPARD. 453 



(a) The relative shortness of the corpus callosum, a structure which, for instance, in 

 the cat, at a corresponding stage of development has assumed a much longer 

 antero-posterior measurement ; moreover, it would seem that in this Seal 

 embryo the corpus callosum is taking a more vertical course than is usual. 



(6) Altogether the general appearance and stage of development of the brain under 

 discussion corresponds very closely with one figured by His * of a three- 

 months human foetus, with the exceptions that the hypophysis cerebri is 

 much further advanced (see infra) and the cerebellum has assumed greater 

 complexity. 



C. Anatomical Details of the Remaining Viscera. 



The thyroid and parathyroids, the thymus, pancreas, and tongue, will be described 

 under the histological section of this pamphlet ; in the present instance the following 

 organs will be considered, and comparisons made with other types, where this is 



possible : 



(i.) The lungs. 



(ii.) The heart. 



(iii.) The liver, stomach, and intestines, 

 (iv.) The spleen. 



(v.) The kidneys and adrenal bodies, 

 (vi.) The genital glands and ducts : the urinary bladder. 



The histology of some of these will be dealt with later. 



(i.) The lungs (PI. III. fig. 3). Both lungs are somewhat compressed against 

 the thoracic walls, owing to the large size of the heart, and it is only upon removing 

 the latter organ that a good view can be obtained of the roots of the lungs and their 

 ventral aspect ; posteriorly the inner margins of the upper and lower lobes of both 

 lungs are grooved longitudinally by the vertebral column, whilst laterally the surfaces 

 of all the lobes are grooved by the ribs. 



In the right lung, three lobes, upper, middle, and lower, can be distinguished t ; 

 the middle lobe is peculiar in that at the root it gives off two caudally directed 

 subdivisions, the largest of which is almost a separate lobe, and presents dorsal, 

 right lateral, and anterior surfaces (PI. III. fig. 3 a). The cranial and caudal lobes 

 of both lungs are somewhat similar in shape, the caudal lobes being the larger, being 

 not unlike the corresponding lobes of a human lung. Marked trabeculse of con- 

 nective tissue are to be seen upon the surfaces of all lobes, with finer strands passing 

 off in all directions, and these subdivide the surface into polygonal areas, the bases, 

 as it were, of the superficial lobules ; on being placed in water the lungs sink. 



At the root of the lung the bronchi and pulmonary vessels are seen entering (or 



* HERTWIG, Handbuch dtr Enticickelungslehre der Wirbeltiere. 



t The terms " upper," etc., are here used with reference to the vertical position of the trunk, and not the natural 

 position of the adult animal. 



(ROY. soc. EDIN. TRANB^ VOL. L., 231.) 



