BRAIN 



53 



lamellfe. On a vertically longitudinal, or " sagittal," section, it has 

 a beautiful tree -like appearance. From the walls of the central 

 cavity branch -like 



white medullary 

 fibres spread out, 

 surrounded by a 

 layer of reddish 

 ganglionic cells, fol- 

 lowed by larger 

 ganglia (Purkinje's 

 layer), and exter- 

 nally covered by a 

 grey mantle of 

 smaller ganglionic 

 cells. Such a thin 

 section, especially 

 when stained with 

 carmine, forms a 

 fascinating object 

 for the microscope, 

 and is easily made. 

 The surface of 

 the cerebral hemi- 

 spheres in Birds 

 exhibits no convol- 

 utions or gyrations 

 as in the higher 

 Mammals. In the 

 Ratitse and in many 

 Passeres the surface 

 is entirely smooth, 

 but in Swimmers, 

 Waders, Pigeons, 

 Fowls, and Birds- 

 of-Prey, there is a 



Twice natural size. 



Venteal view of tiie brain of a Goose. 

 (After A. Meckel.) 

 I-XII, thje twelve pairs of cranial nerves ; Ch. Chiasma of the 

 optic nerves cut across ; Fl. Flocculus ; H. Hypophysis ; X.o.' 

 very slight furrOAV Optlclobe; Lq. Laqueus; F.S. Sylvian fissure; Sp.I. First spinal 

 1 • 1 • 1 , T nerve. 



Avhich 



might 



be 



compared with the Sylvian fissure. There is also very little grey 

 substance in the suxiace layers of the hemispheres. Various attempts 

 have been made, by Tiedemann,i Serres,^ Leuret,^ and Bumm,* to 

 compare the weight of the whole brain Avith that of the body, or 



1 Anatomie unci NaturgeschicMe der Vogel. Heidelberg : 1810. 

 ^ Aiiatomie comparie du cerveau. Paris: 1824. 

 ^ Anatomie con^mree du systeme nerveux. Paris : 1839-57. 

 * Das Grosshirn der Vogel. Zeitschr. fur wissensch. Zool. xxxviii. (1883) 

 pp. 430-466, tabb. xxiv.-xxv. 



