PLATANISTA. 463 



the rigM and left hemisplieres materially differ. What inequality existed, and 

 even the defects from unequal contraction, I have had represented, so that the 

 figures 1, 2, and 3, PI. XXX, faithfiilly pourtray the object. 



The basal surface (Fig. 3) ehcitates the peculiarities of the origin of the cranial 

 nerves. The olfactory bulb does not appear to exist in that area, although the cast 

 shows a protuberance. The optic commissure is relatively feebly represented, 

 although its presence in the depression of the lamina cinerea is distinct. What is still 

 more singular is the extraordinary diminutive pair of optic nerves (5) themselves. 

 These are scarcely, if at all, thicker than an ordinary sewing thread. Indeed, it 

 required a close searching observation to detect them, and the greatest care and skill 

 in manipulation to trace them ; for in raising the membranes the chances of breaking 

 them across were great. But I succeeded in following them iip to the veiy 

 minute perforations by which they entered and passed through in the skull. To 

 the optic foramen I shall again refer in my description of the constituent bones of 

 the cranium. 



The pituitary body (j)) is of considerable size ; even after having been preserved 

 in spirit it retained a comparatively large magnitude. It is of an elliptical or 

 transversely oval figure, 0"50 by 0"25 inch in its opposite diameters, and is of a firm 

 consistence. Two united elevated bodies (a), immediately behind it, appear to be 

 corpora albicantia. The precise conditions of these and their relations to the third 

 pair of nerves I could not ascertain ; for the membranes and large vascular plexus 

 interfered with a correct interpretation of the parts ; hence, as indistinctness pre- 

 vailed, I have omitted in the figure (Kg. 3) the third and fom'th pairs of nerves. 

 In connection with this difiiculty of demonstrating the existence of these nerves, it 

 is interesting to bear in mind that I have ascertained the muscles of the eye-ball 

 to be only rudimentary. 



As to the trifacial or fifth pair of nerves (5), these are very conspicuous; both 

 f ascicuh constituting the roots being easily determinable, and their superficial origin, as 

 usual, referable to the area of the crus of the cerebellum. The filaments comj)osing 

 the posterior root are stout coarse and very numerous. About half an inch or 

 thereabouts from the superficial origin of the nerves is the broad flat and large 

 Gasserian ganghon, but the branches from it and the further distribution of the 

 nerves were not pursued. 



Close beliind the fifth, and therefore possibly a little more laterally than in the 

 higher mammals, there is a good-sized cord of the sixth nerve (6). 



Judging from the origin and relative position, namely, almost abreast of the 

 sixth nerve, and to the sides apparently joining the pons Varolii to the medulla 

 oblongata, there springs laterally the enormously large nerve cords of the seventh 

 pair (7). At the hinder border of each a much thinner nerve is closely applied, 

 but not quite correctly shown in fig. 3. If tliis interpretation be correct, — and I have 

 every reason to believe it so, seeing that Tiedemann and others admit there is a 

 large acoustic nerve in the Dolphin {Delphinus delpliis), — then JPlatanista agrees 

 in this particular, and adds one more fact to the general proposition, that the 



