AMPHIBIA. 



BRAIN. In the turtle the anterior lobes of the brain are large, and contain 

 capacious lateral ventricles ; in each of them there is a large striated body and a 

 choroid plexus ; behind these, and not in the ventricles, there are small thalami joined 

 by a tough commissure ; there is also an anterior and posterior commissure ; more 

 posteriorly the optic lobes are situated, which have ventricles continuous with the lateral 

 and with that of the cerebellum. There is a pineal gland, and the brain is enveloped 

 in a very dense pia mater. The fourth ventricle extends to the calamus scriptorius, 

 and on its floor there are very prominent ventricular cords. The cerebellum is smooth 

 and round, and has neither lobes nor convolutions ; it has a capacious ventricle, so 

 that its parietes are very thin. Its base is very plain, there are no mammillary 

 eminences, and the oblong medulla extends to the spinal cord without much 

 variation in appearance. In the snake the anterior lobes of the brain are of a 

 moderate size, and contain lateral ventricles ; in each of them the striated body and 

 an oblong eminence near the middle line are seen, as in the turtle ; behind these 

 are the optic lobes, and their inner surface forms the continuations from the lateral 

 ventricles to the calamus scriptorius. The cerebellum is remarkably small and flat ; 

 at the base the parts are plain, and similar to those in the turtle. In the frog there 

 are anterior lobes of the brain, and thalami placed externally, optic lobes, and a very 

 diminutive cerebellum, consisting of a narrow transverse band. 



CEREBRAL NERVES. In the turtle the olfactory nerve proceeds from the 

 anterior lobe of the brain ; it is composed of coarse fibrils, which preserve this character 



F 2 



