RETROSPECT AND CONCLUSIONS 157 



which clearly indicates the activity of a higher centre in the 

 nervous system controlling the response received from the visual 

 field. 



We have elaborated the subject of protective coloration in 

 flat-fishes, because it forms a good illustration of the relation of one 

 of the special senses to the brain pattern. Both the naked-eye 

 and microscopic appearances of the optic lobes of plaice and lemon- 

 sole show a very striking develoiiment, and this is clearly related to 

 the great importance of sight both in pursuit of their prey and in 

 provichng protection from their enemies through adaptation of their 

 markings to their surroundings. 



We approach the subject of the cerebellum with some trepidation 

 tempered, however, with some confidence and conviction, that the 

 methods of comparative anatomy which have been so valuable in 

 the study of the medulla oblongata will tlu'ow some light on a 

 hitherto very obscure subject. 



It will be convenient to treat the cerebellum by compartments, 

 remembering that there is a great overlapping of the areas devoted 

 to their different functions. I, consists of the central lobe which 

 may be globular or ovoid and at times is prolonged posteriorly 

 into a long tongue-shaped extension wliich overlaps the medulla ; 

 this lobe has a molecular layer enclosing a granular layer with its 

 superficial ring of scattered Purkinjecells. II, on either side of the 

 base of the cerebelkmi are the acoustic tubercles or acustico-lateralis 

 areas, which some text-books still refer to as the restiform bodies ; 

 these are described as a pair of prominent cord-like masses of nerve 

 tissue on the dorsal surface of the medulla oblongata, forming 

 lateral boundaries of the fourth ventricle and are continued up- 

 wards as the posterior peduncles of the cerebellum. Ill, posteriorly 

 at the base of the cerebellum, lying medially between these ped- 

 uncles is an area of small-celled dark-staining tissue, interspersed 

 with transverse fibres, wliich at times forms a definite lobe, pro- 

 jecting backwards as in the herring, but in the carps either forms 

 a transverse bulge or a well-defined area, known as the central 

 acoustic area. IV, anteriorly the cerebellum gives off a protrusion 

 from its base, which projects into the cavity enclosed anteriorly 

 by the tecta-optica, known as the valvula ; this we have recently 

 discussed, in describing the optic lobes, as sometimes causing a 

 wide separation of the tecta optica. 



It will now be our object to consider the functions of each of 

 these four departments as they can with some accuracy be called. 

 Recently a distinguished surgeon and neurologist remarked to the 

 writer how little was known about the functions of the cerebellum 



