2 'Journal of Comparative Neurology and Psychology. _ 



investigators, working with the teleosts as a rule on account of 

 their greater accessibility, found great difficulty in interpreting 

 the fore-brain centers, the ependymal parts of which were not yet 

 known, until after Rabl Ruckhard's discovery. Some of the 

 authors considered the solid lobes or hemispheres as corpus 

 striatum, and Tiedemann and Arsaky correctly considered the 

 lobi optici as homologous with the corpora quadrigemina of 

 mammals. 



The majority of the others, however, struck by the resemblance 

 of the roof of the optic lobes to the hemispheres of young mam- 

 mals, considered them to be the hemispheres, interpreting the lobi 

 anteriores as the olfactory lobes. It was especially Cuvier who 

 several times expressed this opinion, which after him was accepted 

 by Weber, Kuhl, Treviranus (in his first publication), Fenner 

 and Valenciennes. Serres, however, studying the embryology 

 of the brain accepted Arsaky's and Tiedemann's interpretation 

 and so did Magendie and Desmoulins. The other interpreta- 

 tion, however, was not overcome by their work, and the injury 

 done by Cuvier's errors is clearly shown by Gottsche's work, 

 who agreed in considering the-optic lobes as the hemispheres, and 

 consequently the torus longitudinalis as fornix and the valvula 

 cerebelli as the corpora quadrigemina. 



Von Baer, again reviewing Gottsche's statements, declared 

 the torus longitudinalis to be a structure peculiar to the mid- 

 brain roof of fishes and made a general division of the brain into 

 fore-brain, 'tween-brain, mid-brain, hind-brain and after-brain, 

 which is still current. He, Johannes Muller, Wagner and 

 Stannius contributed very much to the exact knowledge of the 

 central and peripheral nervous system in different groups of 

 fishes. 



A great technical impetus was given by Hannover, who in 

 1844 introduced chromic acid for staining purposes, and by 

 Heinrich MiJLLER, who in 1859 introduced the chrome salts, 

 especially the bichromate of potash, which afterward, combined 

 with Weigert's staining method, created a new era in neuro- 

 logical work. 



Almost all workers, however, in the first years after Hannover 

 dealt with the macroscopic aspect of the brain and peripheral 

 nerves. The work of Busch, Klaatsch, Carus and Mayer 

 conformed to the opinions of Arsaky, Serres and von Baer. 



