. The development of the chick; an introduction to embryology . reach the i^ase of the fore-brain over which they spieadout, entering the olfactory lobe about the sixth day (Figs. 155and 15G). In the meantime the peripheral ends of the olfactoryneuroblasts have extended out as broad protoplasmic processesto the surface of the olfactory epithelium, and thus form the i:!er-cipient ])art of the olfactory Fig. 155. — Olfactory epithelium of a chick embryo of 5days, prepareil by the method of Ciolgi. (After Disse.)a, b, and c indicate different forms of neurobU^sts in theolfactory e|)
. The development of the chick; an introduction to embryology . reach the i^ase of the fore-brain over which they spieadout, entering the olfactory lobe about the sixth day (Figs. 155and 15G). In the meantime the peripheral ends of the olfactoryneuroblasts have extended out as broad protoplasmic processesto the surface of the olfactory epithelium, and thus form the i:!er-cipient ])art of the olfactory Fig. 155. — Olfactory epithelium of a chick embryo of 5days, prepareil by the method of Ciolgi. (After Disse.)a, b, and c indicate different forms of neurobU^sts in theolfactory e|)ithelium. The epithelial cells between fore-brain and olfactory pit, throughwhich the axones of the olfactory neuroblasts grow, are for themost part supporting and sheath-cells of the nerve, but they in-clude a few bipolar neuroblasts (Fig. 156). The latter are tobe considered as olfactory neuroblasts with elongated protoplas-mic processes. Hul)aschkin finds a ganglion, which he calls ganglion olfactoriuninervi trigeniini, situat(M[ iKMicath the olfactory e|)itheliuin in a nine-day chick. The bipolar cells send out pr()cess(\s peripherally which endin fine hianclies l)et\veen the cells of the olfactory mucous membrane,and centrally, which go by way of the ramus olfactorius nervitrigemini towards the (lasserian ganglion. 2. The Second Cm nidi or ()]>lic N^crvc. The course of tliis THE NERVOUS SYSTEM 265
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