SPECIAL CUTANEOUS SUBDIVISION. 141 



correlation inconsistent with its serving primary sensory nerves. 

 On the other hand, some fibers of the cochlear nerve go beyond 

 its primary nuclei, by way of the corpus trapezoideum and the 

 secondary tracts, to higher centers. The fibers arising in the two 

 cochlear nuclei go by a direct or indirect course chiefly to the 

 lateral lemniscus of the same or opposite side (p. 258). The 

 main facts with regard to the central connections of the cochlear 

 and vestibular nerves are shown in the most diagrammatic form 

 in Fig. 70, in order to facilitate comparison with the arrangements 

 in lower vertebrates (Fig. 69). The further consideration of the 

 central relations will be more appropriate in the chapter on the 

 correlating centers. 



DEMONSTRATION OR LABORATORY WORK. 



1. Dissect the lateral line system and ear and their nerves in the 

 dogfish or skate. 



2. Study sections of lateral line organs from a selachian or from 

 teleost embryos, stained with iron haematoxylin or prepared by a 

 special nerve method. 



3. Review the dissection of the selachian and teleost brain (Chap- 

 ter II, No. 2 and Chapter V, No. 2) with reference to the great 

 development of the acusticum and cerebellum in selachians, and the 

 correlation with the large number of acustico-lateral organs. 



4. Study the roots of the acustico-lateral system of nerves in the 

 brain of a selachian or ganoid fish in Weigert or Golgi sections. 



5. In Golgi sections of a fish brain study cells of acusticum and 

 cerebellum to follow the evolution of the Purkinje cells. Notice the 

 granules and cells of type II. 



6. In Weigert or Golgi sections of a fish brain note the internal 

 arcuate fibers to the lemniscus system. 



LITERATURE. 



Allis, E. P., jr.: Lateral Line System in Amia. Jour. Morp., Vol. 2. 1889. 



Ayers, H. : Vertebrate Cephalogenesis II. A Contribution to the Mor- 

 phology of the Vertebrate Ear, with a Reconsideration of its Functions. 

 Jour. Morph., Vol. 6. 1892. 



Barker, L. F.: The Nervous System and its Constituent Neurones. 1899. 



Beard, J. : On the Segmental Sense Organs of the Lateral Line and the 

 Morphology of the Vertebrate Auditory Organ. Zool. Anz.. Jahrg. 7. 1884. 



Brauer, A.: Beitrage zur Kenntniss der Entwickelung und Anatomic der 

 Gymnophionen. Zool. Jahrb., Suppl. 7. 1904. 



