THE MEDULLA OBLONGATA AND CEREBELLUM 159 



best be understood by considering each functional system of 

 fibers as a unit and studying the connections of each component 

 separately. These connections are summarized in a table on pp. 

 146, 147. The medulla oblongata of lower vertebrates and of 

 the human embryo is seen to be composed chiefly of the primary 

 centers related to these functional components of the peripheral 

 nerves, arranged in longitudinal columns in the order from dorsal 

 to ventral surfaces on each side of somatic sensory, visceral 

 sensory, visceral motor, somatic motor centers. The same 

 arrangement appears in the adult human oblongata, though 

 somewhat distorted by the presence of large masses of correla- 

 tion tissue and of large conduction tracts which are not present 

 in the lower vertebrates. The sensory centers of the oblongata 

 are connected locally with the adjacent motor centers and also 

 by longer tracts with the spinal cord, cerebellum, and thalamus. 

 The latter fibers constitute the bulbar lemniscus, of which several 

 functional components can be distinguished, the most important 

 being the trigeminal lemniscus for general cutaneous sensibility 

 and the lateral or acoustic lemniscus for auditory sensibility. 

 The cerebellum is a proprioceptive center developed, out of the 

 vestibular area of the medulla oblongata. 



LITERATURE 



The details of the structure and functions of the parts mentioned in this 

 and the following chapters will be found fully presented in the standard text- 

 books of human anatomy and physiology and in the medical text-books of 

 neurology, and all of this literature up to the year 1899 is summarized in 

 Barker's Nervous System and Its Constituent Neurones. See also W. 

 von Bechterew, Die Funktionen der Nervencentra, Jena, 1908 to 1911, 

 3 vols. For discussions of comparative neurology and the evolution of the 

 nervous system, reference may be made to articles in the neurological 

 journals, especially the Journal of Comparative Neurology; see also the 

 Bibliographies on pp. 36, 124, 193, and 223, and the following works: 



HERRICK, C. JUDSON. 1899. The Cranial and First Spinal Nerves of 

 Menidia: A Contribution Upon the Nerve Components of the Bony Fishes, 

 Jour. Comp. Neurology, vol. ix., pp. 153-455. 



. 1913. Brain Anatomy, Wood's Reference Handbook of the Medical 

 Sciences, 3d ed., vol. ii, pp. 274-342. 



. 1914. Cranial Nerves, ibid., vol. iii, pp. 321-339. 



JOHNSTON, J. B. 1906. The Nervous System of Vertebrates, Philadel- 

 phia. 



. 1909. The Central Nervous System of Vertebrates, Spengel's 

 Ergebnisse und Fortschritte der Zoologie, Bd. 2. Heft 2, Jena. 



EDINGER, L. 1908. Vorlesungen iiber den Ban der nervosen Zentral- 

 organe, 7th Auflage, Band 2, Vergleichende Anatomic des Gehirns, Leipzig. 



. 1911. Idem, 8th Auflage, Band 1. 



