X Journal of Comparative Neurology. 



Koelliker on the Brains of Monotrenies.' 



Under this title Professor Kolliker treats the indicated portion 

 of the brains of Ornithorhynchus and Echidna separately, about two 

 thirds of the space being given to the former. In both cases the meth- 

 od of treatment is the same : a description of a series of transverse 

 sections (i8 of Ornithorhynchus and 9 of Echidna) followed by a de- 

 scriptive and comparative study of the particular parts as they appear 

 throughout the section-series. In his resume of results the author calls 

 attention to the following important features : The fourth ventricle is 

 proportionately much longer than in other mammals. The pyramidal 

 decussation is very feebly developed and the pyramidal tracts, indistin- 

 guishable anteriorly, are at best ill defined in the posterior parts of the 

 medulla. The more distal course of the fibers is either in the "Seiten- 

 strang" or in Burdach's column. There is a typical fillet which is stronger 

 in Echidna than in Ornithorhynchus, while the nucleus gracilis in both 

 animals is small as compared with the nucleus of Burdach's column. 

 The "nucleus lateralis" (n. of lateral tract in the medulla) is much 

 better developed in Echidna than in Ornithorhynchus. The nucleus 

 of the hypoglossus, as compared with that of other mammals, is located 

 much more laterally, and the root fibers pass " medio- ventralwarts" to 

 their exit. The accessorius is much stronger in Echidna than in Orni- 

 thorhynchus. Its root fibers penetrate the tuberculum quinti in 

 Echidna while in Ornithorhynchus they pass first between the "fasci- 

 culus lateralis" and the tuberculum quinti and then penetrate the latter. 

 The nucleus ambiguus and the end nucleus of the fasciculus solitarius 

 are very strongly developed in Echidna. The nervus cochlearis enters 

 the medulla with the nervus vestibularis ventrally of the posterior cere- 

 bellar peduncle. The acustic nerve is very large in Echidna and very 

 small in Ornithorhynchus. There occur in both animals two distinct 

 facial motor nuclei, a dorsal and a ventral, while the former in Echidna 

 shows a tendency to separate into four groups of cells. The facial 

 nerve is small in Ornithorhynchus and large in Echidna. A longitudi- 

 nal spino-cerebral tract, the "Zonalbahn," associated posteriorly with 

 the quintus descendens, joins the "Bindearm" in Echidna but is ab- 

 sent in Ornithorhynchus. The oculomotor nucleus in a single group 

 of cells without crossed fibers. The inter-olivary lemniscus medialis is 

 composed of fibers from the fillet, secondary trigeminal fibers, and 



'A. Koi.LiKER. Die Medulla Oblongata und die Vierhugelgegend von 

 Ornithorhynchus und Echidna, "mit 27 zum Thiel farbigen Abbildungen im 

 Text," 100 pp. quarto. Leipzig, 1901. Wilhelm Engelmann, 16 M. 



