DESCRIPTIONS OF PREPARATIONS. 



1. Common Eat {Mus Decumanus), 



Dissected so as to show its craniospinal nervous axis in its entire length as well as 

 » portions of most of the organs of vegetative life. 



A RED injection has been thrown into the veins, and the left 

 halves of the walls of the craniospinal, thoracic, abdominal, and 

 pelvic cavities, as well as the greater part of the integument 

 in the facial region and the greater part of the left lung, have 

 been removed so as to show in siiic the organs previously concealed 

 by these structures. 



Of the encephalic nerve-centres we see most anteriorly the 

 olfactory lobes : next to them the cerebral, separated from each 

 other by the longitudinal fissure in which is lodged the longitu- 

 dinal sinus : next the cerebellum bounded off anteriorly from the 

 posterior border of the cerebral ovoids by the diverging lateral 

 sinuses, into which the longitudinal sinus divides. The presence of 

 the lateral sinuses prevents us from seeing the corpora quadri- 

 gemina which would otherwise be visible » in the middle line, 

 owing to the divergence there from each other of the cerebral 

 lobes. The medulla oblongata, which is, like the cerebellum, of 

 considerable width, comes into view between the two occipital 

 condyles, from which point down to the second dorsal vertebra, 

 recognizable by its long spine carrying an ossicle articulated to its 

 apex, the medulla spinalis is of much greater thickness than it 

 attains posteriorly. It is seen in the lumbar region to break up 

 into the cauda equina. 



In the dorsal region, a black bristle has been passed under the 

 aorta where it underlies the bodies of the vertebrae, and this position 



* For the relations held by the cerebrum and cerebellum to each other and to the 

 tentorium, see Turner, 'Proceedings Royal Society »»r Edinburgli,' March 3, 1862. 



