8 30 



A MANUAL OF PHYSIOLOGY 



less be mentioned as milestones in the march of development. The 

 pineal body is made up of the vestiges of the unpaired mesial eye of 

 such animals as the ancient labyrinthodonts, which resembled the 

 eye of invertebrates in having the retinal rods directed towards 

 the cavity instead of towards the circumference of the eyeball. In 

 many living forms, especially in certain lizards, this pineal or 

 parietal eye is found in a more perfect condition, though covered 

 by a thin membrane. The ganglia habenulce, two small collections 

 of nerve-cells, one of which is situated at the posterior part of each 

 thalamus, are supposed by some authorities to represent the optic 



ganglia of this cyclopean eye. 

 They are less prominent in 

 man than in many of the 

 lower animals. The infundi- 

 bulum is probably what re- 

 mains of the gullet of the 

 ancestors of the vertebrates. 

 The pituitary body is in a 

 different category. It is now 

 known that, far from being 

 a useless vestigial remnant, 

 it has a highly important 

 function (p. 566). It con- 

 sists of two portions, the 

 anterior lobe, or hypophysis, 

 derived from the buccal 

 cavity, the posterior lobe, 

 or infundibular body, from 

 the primary fore-brain. 



Functions of the Cere- 

 bellum. The elaborate 

 pattern of the arbor vitae, 

 the appearance given by 

 the branched laminae in a 

 section of the cerebellum, 

 excited the speculation of 

 the old anatomists. A 

 structure so marvellous 



FIG. 346. CEREBELLAR CORTEX : SECTION 

 IN DIRECTION OF LAMINA (CAJAL). 



a, Purkinje's cell ; b, granule cell in inner 



layer ; c, dendrite of a granule cell ; d, axon mu st be matched, they 



of a granule passing into the molecular t u oll ~u t w : f u f linr tion<; 

 layer, where it bifurcates into two fine MIgnt, Wltn 



longitudinal branches (Golgi's method). as unique. At a time 



when the discoveries of 



Galvani and Volt a were fresh, and the world ran mad on 

 electricity, the hypothesis of Rolando, that ' nerve-force ' 

 was generated by the lamellae of the cerebellum as electrical 

 energy is generated by the plates of the voltaic pile, ridiculous 

 as it now appears, was not unnatural. The speculation of Gall, 

 who connected the cerebellum with the development of sexual 

 emotions and the action of the generative mechanisms, was 

 based on no fact. It has been definitely disproved by the 

 observations of Luciani, who found that a bitch deprived of 



