THE NERVOUS SYSTEM. 531 



disappearance of that portion of the axone distal to the point of injury; it may 

 also lead to the disappearance of the entire neurone where regeneration is not 

 possible. Such an injury during development will not only cause a disappear- 

 ance of the whole neurone, but it may also lead to the disappearance of other 

 neurones forming links in the same functional pathway. Thus a develop- 

 mental defect involving the central area will not only lead to absence of the 

 pyramidal tract, but also to partial atrophy of the corresponding fillet bundles. 

 When one cerebellar hemisphere fails to develop, there results a correlated 

 defect in its centripetal and centrifugal pathways. The opposite inferior olive 

 is practically absent, as is also the central tegmental tract leading to that olive. 

 The pontile nuclei of the opposite side, the middle peduncle leading from them 

 to the affected cerebellar hemisphere, and the fibers in the pes which pass to 

 the pontile nuclei in question are likewise suppressed, and the superior 

 peduncle and red nucleus are absent or reduced. In this case it is evident that 

 the correlated atrophy affects at least two neurones in the pathways leading to 

 and from the cerebellum. This illustrates the far-reaching character of cor- 

 related developmental defects in the nervous system arising from the nature 

 of the connections between various portions of the system. 



References for Further Study. 



BARDEEN, C. R.: The Growth and Histogenesis of the Cerebrospinal Nerves in Mam- 

 mals. Am. Jour, of Anat., Vol. II, No. 2, 1903. 



DEJERINE, J.: Anatomic des centres nerveux. Tome I, Ch. 2 and 3. 



EDINGER, L.: Vorlesungen iiber den Bau der nervosen Zentralorgane. Seventh Ed. 



EDINGER, L. The Relations of Comparative Anatomy to Comparative Psychology. 

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FLECHSIG, P. : Einige Bemerkungen iiber die Untersuchungsmethoden der Grosshirnrinde 

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45-49. 



HARDESTY, I. : On the Development and Nature of the Neuroglia. Am. Jour, of Anat., 



Vol. Ill, No. 3, July, 1904. 



HARRISON, R. G. : Further Experiments on the Development of Peripheral Nerves. 

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HARRISON, R. G.: Observations on the Living Developing Nerve Fiber. Anat. Record. 



Vol. I, No. 5, 1907. 



HARRISON, R. G.: Embryonic Transplantation and Development of the Nervous 



System. Anat. Record, Vol. II, No. 9, 1908. 



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His, W.: Zur Geschichte des menschlichen Riickenmarkes und der Nervenwurzeln. 

 Abhandl. der math.-phys. Klasse der Konig. -Sachs. Gesellsch. d. Wissensch., Bd. XIII, 1887. 



His W Zur Geschichte des Gehirns, sowie der centralen und periphenschen Nerven 

 bahnen' beim menschlichen Embryo. Abhandl. d. math.-phys. Klasse d. Konig.-Sachs. 

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