442 



ANATOMICAL TECHNOLOGY. 



(B) the cephalo-caudal extent of the latter; (C) the manner of cleavage of the heml 

 spheres ; (D) the irregular lamination of the cerebellum. 



Preparation. The hemispheres and Ldbi olfactorii of a hardened brain were sliced to 

 near the level of the callosum and in a plane coinciding with the larger part of its course. 



The slight portions overhanging the borders of the 

 callosum so as to constitute the FF. callosales (Fig. 116, 

 122; PI. Ill, Fig. 33) were then pushed dorso laterad 

 with the tracer ; the torn surfaces so left are repre- 

 sented by the striated areas. On the right, a part of 

 the hemisphere was torn off so as to indicate the wave- 

 like arrangement of the fasciculi. 



An oblique section was then made from opposite 

 the splenium through the caudal portion of the hemi- 

 spheres and the cerebellum, so as to expose the post- 

 optici. 



Explanation. The name is written lengthwise of 

 the callosum ; perhaps the line at each side represents 

 a stria longitudinalis. The curvature ventrad at the 

 genu and splenium is better shown in section (Fig. 

 116; PI. II, Fig. 14). The postoptici do not appear 

 distinctly, and no attempt was made to indicate the 

 areas of cerebral alba and cinerea, or of the pes, pero 

 or coelia in the rhinencephalon. 



1132. Preliminary Examination of the Basis 

 Encephali. As seen in Fig. 116, 118, and PI. II, 

 Fig. 3, the base of the brain presents numerous parts 

 distinguished by their elevation, their subdivision, 



their color or the direction of their fibers. Including the twelve cranial nerves, about 

 fifty different parts, more or less comprehensive, are named upon Fig, 116. 



The cranial nerves are treated of in the next chapter. Of the remaining parts, the 

 beginner is advised to study first only those which have been observed in the Amphibian 

 brain, or which serve either as topographical landmarks or as aids in recognizing the limits 

 of the encephalic segments. Later, it will be desirable to identify each feature by the aid 

 of the figures (Fig. 118 , PI. II, Fig. 3 ; PI. Ill, Fig. 11) and the detailed descriptions. 

 Fig. 116. Diagram of the base of the brain, including the nerve roots. 

 Explanation. The names are written in full. As suggested above, the following 

 parts are to be noted first : 



Myelon, expanding into the metencephalon. 

 Cerebellum, greatly enlarged and convoluted. 

 Hemisphasrae, still more enlarged and likewise convoluted. 

 Lobi olfactorii, elongated and in apposition, but not organically united. 

 Chiasma, Tuber cinereum, infundibulum, hypophysis, Crura cerebri (one of which 

 is designated on Fig. 116 by the word crus) and pons. 



Of the parts just named, all but the last have been noted upon the mesal aspect of the 

 Amphibian brain, and are mentioned in the Table ( 1069). 



The pons is a wide and thick band of transverse fibers connecting the lateral lobes of 

 the cerebellum across the ventrimeson. It is likewise a prominent landmark, serving, 

 with the chiasma, to divide the entire basis encephali conveniently into three general 

 regions caudal, Area postpontilis ; cephalic, Area praechiasmatica ; and intermediate, 

 Area cruralis. 



FIG. 115. DORSAL ASPECT OF 

 THE CALLOSUM AFTER PAR- 

 TIAL REMOVAL OF THE 

 HEMISPHERES ; x 1. 



