THE BRAIN. 243 



are fused as far as the middle, Alcedo (e) ; pedes insidentes (/), the 

 inner toe is behind, the three anteriorly directed toes are united by 

 a short membrane, Falco (f). Sometimes the outer toes of the 

 pes scansorius (Cumulus), and the inner toe of the pes adhamans 

 (Colius) can be turned both forwards and backwards^ The_wading 

 legs (p. vadantes) as opposed to the walking legs (p. gradarii) are 

 characterised by the partly or completely naked, unfeathered tibial 

 region ; v they are found principally in Water Birds, amongst which 

 the Grallatores have wading legs with a very long metatarsus the 

 so-called pedes grallarii. The p. grallarii may be distinguished into 

 p. colligati, in which the anterior toes are united at their roots by a 

 short membrane, Ciconia (g) ; and the p. semicolligati, in which this 

 membranous connection is confined to the middle and outer toes, 

 Limosa. The running legs (p. cursorii) are powerful pedes grallarii 

 without hind toes, and with three (Rhea) or two Struthio (h) strong 

 front toes. The short wading legs of the swimming birds, as well as 

 the longer legs of the Grallatores, present with regard to the structure 

 of their feet the following types : Swimming feet, or pedes palmati, 

 when the three anteriorly directed toes are connected as far as their 

 extremities by an undivided swimming membrane or web, Anas (i) ; 

 half swimming feet, or p. semipalmati, when the web only reaches to 

 the middle of the toes, Recurvirostra (k) ; split swimming feet, or p. 

 fissipalmati, when the toes have an entire cutaneous border, Podiceps 

 (1) -, lobed feet, or p. lobati, when the border is lobed on each joint, 

 Fulica (m). When the hind toe is also included in the web mem- 

 brane the feet are termed p. stegani, Halieus [Phalacrocorax] (n). 

 Finally, the hind toe may be reduced or completely absent in the 

 Natatores and Grallatores. 



The Brain of Birds (fig. 79) is much more highly developed than 

 that of Eeptiles, and completely fills the roomy cranial cavity. The 

 hemispheres are, indeed, still without superficial convolutions, but 

 s/already possess a rudimentary corpus callosum (Meckel). They cover 

 not only the thalamencephalon, but also the two large, laterally 

 displaced corpora bigemina. The differentiation of the cerebellum is 

 still further advanced, since there is a median part corresponding to 

 the so-called vermis of Mammalia, and small lateral appendages. 



Tn consequence of the cervical flexure of the embryo the medulla 

 oblongata forms an angle with the spinal cord, the posterior columns 

 of which diverge from one another in the posterior enlargement of 

 the lumbar region so as to form a second sinus rhomboidalis. The cranial 

 nerves are all separate and their distribution is essentially the same 



