11 



all comparative anatoicists through their reproduction in the 

 text-books. The histological portion oi" the research is care- 

 fully vyritten, and it is clear that the writer had seen all 

 that the technique of the period would demonstrate. We find 

 in his f injures, therefore, nerve-eel J s represented with some 

 detail of structure, nerve-fibres showing soire connection with 

 particular groups of nerve-cells, and fibre-tracts which take 

 a certain definiteness in their courses. The most noteworthy 

 discovery made by Rohon was the iachkerne of the midbrain; see 

 Section VI. But the greatest service which he has rendered 

 consisted in his pointing out for the first time the many struct- 

 ural features which the brain of the selachian has in common 

 with the organisation of higher vertebrate brains. 



The next research which we have to notice is that of Sanders 

 ('3*). This author seems not to have been familiar with the 

 great advances Just made in methods of research, (see infra); 

 and so we find him rejecting carmine as a staining medium and 

 expressing a preference for rosaniline because of the clearness 

 of the pictures yielded by it, while he gives a mere hint of 

 haematoxylin. The scale of the work is ambitious to a degree 

 bordering on superficial treatment. There are to be included 

 the anatomy and histology of the brain, spirial cord, and cranial 

 nerves in both the rays and the sharks. The histological descrip- 

 tions usually embrace the general distribution of the nerve-cells 

 of a given region, followed by exhaustive measurements of their 

 si?.es. His figures are hardly more than outlines of brain- 



