394 C. JUDSON HERRICK 



Figs. 4 to IS Fifteen transverse sections through the brain of a 3S mm. hxrva 

 of Amblystoma tigrinum. pre])areil by the silver rechietion method of Ram6n y 

 Cajal. Those drawings were made from the same series of sections used in the 

 construction of the model shown in figures 1 to 3. In the following descriptions the 

 serial number of each section figured is given. By comparison with the scales 

 accompanying figures 1 to 3 the exact place of the section figured in the model can 

 be determined, the sections being 15/x thick. The drawings were outlined with 

 the Edinger projection apjiaratus, and in projection the image was reversed so as 

 to permit a direct comparison of the drawing with the appearance of the prepara- 

 tion under the compound microscope. The mirror-image of these drawings would, 

 therefore, give the correct relations. In the model, figures 1 to 3, the natural 

 relations of right and left sides are preserved, so that figures 4 to 18, though 

 apparently representing the right side of the brain, should be compared with the 

 left side of the model. The two sides of the specimen figured are in all essential 

 respects similar, save for slight differences in the arrangement of the vagus roots 

 at their superficial origins. The nuclei of the cells of the stratum griseum are 

 drawn as clear circles, those of the scattered cells of the stratum album as black 

 discs. These latter nuclei, which are of uncertain significance, stain darker in 

 these preparations than those of the stratum griseum. Some of the larger neurones 

 of the motor nuclei of the cranial nerves and of the marginal zone of the gray layer 

 are drawn with shaded nuclei and clear cytoplasm. The topographical relations 

 of the fiber tracts of the stratum album are drawn as faithfully as possible, but the 

 texture of these tracts is schematically indicated to facilitate following each tract 

 through the series of sections. 



Fig. 4 Section 245, through the caudal part of the midbrain immediately in 

 front of the nucleus posterior tecti. The cell bodies of this nucleus lie farther 

 caudad; the dendrites of these cells extend forward into the neuropil marked 

 nuc.p.t., which also receives terminals of the tractus bulbo-tectalis (tr.b.t.). The 

 section also includes the rostral end of the cminentia subcerebellaris tegmenti 

 (em.s.t.). 



Fig. 5 Section 255, through the nucleus posterior tecti {nuc.p.t.) above and the 

 pedunculus cerebri below, immediately rostral to the auricular lobes, cutting 

 through the eminentia subcerebellaris tegmenti {em.s.t.) at its widest part. 



Fig. 6 Section 260, through the rostral end of the auricular lobe {lob. au.), 

 including the terminals of the ascending roots of the V and VIII cranial nerves. 

 The plane of section of figure 52 is indicated by guide lines. 



