28 journal of Comparative Neurology and Psychology. 



better seen as a distinct attachment between the corpus genicu- 

 latum laterale and the medial wall. 



Meanwhile the fibers of a small but compact and rather heavily 

 medullated commissure which lies close under the wall of the 

 ventricle (Fig. xxxvi) pass upward and laterally where they enter 

 the tectum near the corpus geniculatum laterale. This is Her- 

 rick's commissura minor, which, as already observed, is accom- 

 panied by the medial opticus fibers and some fibrae ansulatae. 

 This commissure Edinger, Goldstein and I have agreed to 

 name in honor of the excellent American neurologist, Herrick's 

 commissure It may be that it terminates in small part in the 

 ganglion into which a few of the opticus fibers seem to enter, but 

 by far the greater part passes under the brachium laterale through 

 the upper layer of the tectum opticum. Accordingly, there is no 

 doubt whatever that this commissure terminates for the greater 

 part, if not wholly, in the tectum opticum. Moreover Herrick, 

 who first gave a description of this connection, observes that he 

 lost sight of it at the point where the lateral optic radix enters the 

 tectum. 



The reason for the much greater size of the brachium laterale 

 tecti as compared with the brachium mediale appears in the sec- 

 tions farther caudad. The brachium laterale extends in two 

 branches over the whole dorso-lateral tectum; the dorsal branch 

 is the one that first becomes visible in frontal sections, and from 

 the same stem a latero-ventral branch is given off which may be 

 seen along the right half of the tectum far posterior. Presently 

 it disappears under the faintly colored fibers of the ventral opticus 

 bundle which passes laterally over the tectum and with which it 

 runs into the most caudo-lateral part of the mid-brain roof (Figs. 

 xliii to xlvi). In these last sections we see the loops of the com- 

 missura transversa, now completely united, which end partly in 

 the accumulation of cells under the optic ventricle (^nucleus 

 corttcaUs = nucleus dorsalis thalanii of Goldstein), partly in the 

 nucleus prcerotundus, of which we spoke before. 



In many authors whose works I have read for my investigations 

 I have often wished to have a more systematic reproduction of the 

 sections themselves rather than a very extended text. I have 

 preferred giving many illustrations of this complicated region 

 instead of presenting a description which, of course, would have 

 to be very complicated and which could not present what the sec- 



