58 



ANATOMY OF THE CENTHAL NERVOUS SYSTEM. 



The Froriep fundaments, on the other hand, have an ezclusively embryonic 

 existence, and were, therefore, regarded by their discoverers as ontogenet- 

 ically persistent rudiments of lost ancestral sense-organs; and were called 

 Iranchial cleft organs (Kiemenspaltenorgane). Definite traces of this embry- 

 onic connection with the epidermis are manifest in the adult in the Acustico- 

 facialis, the Glosso-pharyngeus, and Vagus; the KupfEer series corresponds 

 to the Ggl. acusticum, Ggl. jugulare of the IX and the Ggl. jugulare of the 

 X; from the Froriep series arise the Ggl. geniculatum (VII), Ggl. petrosum 

 (IX), and the pneumogastric ganglion (X). 



Va 



.gri- 



(Chord^ /' If;;;. J \\ „ 



Fig. 26a. — Cross-aeetion through the posterior part of the head of a shark 

 embryo, of twelve millimeters' length. The section passes through the fourth 

 visceral cleft (4) and through the vagus ganglion with its two epidermal con- 

 tacts: the Kupffer fundament (Kupffer Anl.) and the Froriep fundament, re- 

 spectively, — the lateral and the epibranehial fundaments, n, a, Arteries, v, 

 Jugular vein. (After Froriep.) 



The olfactory nerve occiipies an exceptional position. At one time 

 its primitive ganglion seemed to be quite absent. The olfactory ganglion of 

 His arises independent of the nasal pit — the KupfEer fundament — as a 

 purely lateral ganglion, migrates away from the nasal pit, approaches the 

 brain, and fuses completely with the olfactory bulb. The nasal pit behaves 

 also in a special way, in so far as it is the only one of the persistent funda- 

 ments which retains the character of the primitive sense-organs. Its cells 

 remain in situ as peripheral nerve-cells which send their neuraxons into the 

 olfactory bulb. In the case of other sense-organs — e.g., the auditory pit — a 

 separation takes place: the original peripheral nerve-cells migrate inward 



