53« 



AMPHIBIA. 



nective tissue. They consist of bundles of muscle fibres, 

 and at their ends or at one of them they are usually con- 

 tinued into strong tendons, which are more or less directly 

 attached to parts of the skeleton. 



For an account of the musculature of Vertebrate types, 

 the student is referred to the guides to practical work cited 

 in the Appendix. 



Fig. 230. — Brain of frog. — After Wiedersheim. 



I. Dorsal Aspect. — o.l., Olfactory lobes ; c.h., cerebral hemi- 

 spheres ; P., pineal body, rising from region of optic thalami ; 

 op. 1., optic lobes ; cb., rudimentary cerebellum ; M.O., medulla 

 oblongata. 

 II. Ventral Aspect. — The numbers indicate the origins of the 

 nerves, ch., Optic chiasma ; T.c, tuber cinereum ; H., hypo- 

 physis. 

 III. Horizontal Section. — l.v., 1 and 2, lateral ventricles of 

 cerebrum; F.m., foramen of Monro; K., 3 and 4, third and 

 fourth ventricles ; Ay., cavities of optic lobes and aqueduct of 

 Sylvius from third to fourth ventricle. 



Nervous system. — The brain, covered with a darkly pig- 

 mented pia mater, has the usual five parts. 



The elongated cerebral hemispheres have "olfactory 

 lobes " in front of them, and are connected by anterior 

 and posterior commissures, and by a hint of a " corpus 

 callosum " (?). 



The thalamencephalon gives origin dorsally to a pineal 

 outgrowth. The pineal body lies outside the skull in 

 the tadpole, but is partially atrophied in the adult, so 

 that little more than the stalk is left. On the ventral 



