viii Journal of Comparative Neurology. 



the same side of the cerebeUum, the greater part of the decussatio cere- 

 belU belongs to this system. The tractus cerebello-thalamicus cruciatus, 

 the. most mesial of the second category, forms into two bundles in the 

 base of the Mittelhirn and, decussating in the region of the oculomo- 

 torius, ends in the gray matter dorsal and lateral of the infundibulum. 

 The tractus cerebello-mesencephalicus passes obliquely to its apparent 

 termination anterior and lateral of the ganglion interpedunculare. Im- 

 mediately upon the termination of these fibers, however, there appears 

 a new bundle which without doubt ends in the nucleus pretectalis. The 

 tractus cerebello-spinalis passes into the cerebellum by an anterior part 

 and a much stronger posterior part. The latter passes directly over 

 the nucleus cerebelli, from which it appears to receive fibers, from the 

 lateral periphery of the medulla. The anterior part of this tract can- 

 not be so certainly followed and may not belong to this system. The 

 fibers of the tractus cerebello-tectalis collect themselves out of the 

 deepest fibers of the Mittelhirn roof and may arise from cells of the 

 nucleus magnocellularis which is usually assigned to the trigeminus. 

 The entire tract disappears in the velum anticum caudal of the decus- 

 sation of the trochlearis and may possibly be a dorsal trochlearis root 

 and not a cerebellar tract. The tractus cerebello-spinalis ventralis is 

 probably represented by the more lateral and larger of the tracts from 

 the decussatio veli, which is dorsal and anterior of the decussation of 

 the trochlearis. This tract passes caudad and ventrad peripherally of 

 the ganglion isthmi into the medulla. From the vagus, glossopharyn- 

 geus, acusticus and trigeminus fibers pass directly into the cerebellum. 

 B. Haller's "obere aussere Wurzel des V." is assigned to the ramus 

 lateralis facialis. This root may not send fibers into the cerebellum 

 proper but its terminal nucleus, in the lobus acustico-facialis, is covered 

 by the true cerebellar cortex so that the essential cerebellar connection 

 probably exists. The author concludes: "dass das Kleinhirn der 

 Selachier im Wesentlichen nur Endstiitte der directen sensorischen 

 Bahn aus den Hirnnerven ist und dass alle anderen in es eingehen- 

 den Fasern nur ein kleine raumliche Rolle spielen." 



In tracing nerve fibers into the cerebellum Professor Edinger has 

 employed successfully the degeneration methods of Marchi and 

 Alghieri. He found difficulty, however, both in securing proper 

 degeneration of the tracts, partly on account of the early death of the 

 specimens, and also in interpreting the degeneration results, since re- 

 gions clearly out of connection with the affected centers showed de- 

 generation phenomena. The latter may in some cases be due to the 

 more active metabolism. g. e. coghill. 



