86 AVES. 



weight of the body, the extensors obtain a manifest preponderance 

 of size over their opponent flexors, and all take their origin high up 

 upon the pelvis. Two glutaei muscles (m. glutaus major ct minor} 

 may be distinguished, the first of these being of tolerably large size, 

 and filling up the external concave surface of the ilium ; there 

 frequently occurs also a third glutaeus muscle. Of the gemelli 

 muscles the superior one is present. The adductor and flexor mus- 

 cles, viz., the rectus femoris, the sartorius which is often wanting 

 e. g. in the Herons, the m. gracihs, biceps femoris and also the tensor 

 vagina, admit of being readily referred to their respective analogues 

 in Man. 



Such is also the case with the remaining flexor and extensor mus- 

 cles of the leg and toes, in which a gastrocnemius, tibialis anticus, 

 peronaus, flexcr digitorum longus perforatus et perforans, can be dis- 

 tinguished, along with special adductors and abductors of the toes. 

 The fleshy portions of all these muscles are situated high up, arising 

 from the proximal end of the tibia, or even from the femur, and arc 

 continued over the rest of the leg, in the form of very long tendons. 

 They exhibit modifications in the foot according as the great toe is 

 present or absent, or there is a fifth toe developed, or in relation to 

 the whole foot, as it may be adapted either for swimming or climb- 

 ing, &c. 



The methods by which the actions of swimming and flying are 

 performed are subjects belonging rather to the physiology and natural 

 history of birds, arid can not therefore be further inquired into in the 

 present work. 



NERVOUS SYSTEM. 



THE same coverings or membranes can be distinguished in the 

 Brain of birds as are met with in that of the human subject. The 

 dura mater, which is of a tough consistence, gives off a feebly de- 

 veloped falx, prolonged from a bony ridge upon the internal surface 

 of the cranial cavity, between the two cerebral hemispheres. A 

 strong fold of this membrane forms also a tentorium between the 

 cerebrum and cerebellum ; and the vascular plexuses of the pia mater 

 are remarkably developed. 



The Hemispheres form a pair of nervous masses usually of the 

 shape which their name implies, but which are, in some cases, as 

 in the Grallae, Palmipedes, and also in the Parrots, more elon- 

 gated longitudinally, than laterally expanded, as in the Birds of 



