346 Journal of Comparative Neurology. 



entered the bulbus the latter acquires, even in the embryo, a 

 very peculiar appearance. 



" As regards the anatomical significance of the elements 

 of the olfactory nerve. His regards them in the embryonic 

 state as bipolar nerve cells, and the nerves themselves as the 

 olfactory ganglion. Furthermore, he states that the greater 

 number of these cells can be re-identified later in the olfac- 

 tory lobe itself. These cells, inasmuch as they were origi- 

 nally epithelium of the nasal pit, have undergone a consider- 

 able migration, so that the question naturally arises whether 

 all the nerve cells of the olfactory ganglion have not gradu- 

 ally entered the bulbus. The solution of the question de- 

 pends upon the interpretation of the histological structure of 

 the olfactory nerve of the adult. If the nuclei of the olfac- 

 tory belong to the nerve fibres, then the peripheral portion 

 of the olfactory is to be regarded as the ganglion; if, on the 

 other hand, these nuclei belong to the sheath, it may 

 be assumed that all the ganglion cells have entered the 

 bulbus. 



" In this discussion His has overlooked my statement, 

 made in 1883 and based on the investigation of a human 

 embryo of the second month, ' that the nucleated fibrillated 

 bundles of the olfactory nerve of embryos are the direct fore- 

 runners of the nucleated pale olfactory fibres of the adult, 

 and therefore are to be compared with the axis-cylinders of 

 other nerves and the nuclei with the nuclei of nerve cells.' 

 Nevertheless, these elements differ from those of a typical 

 ganglion in that each olfactory fibre possesses a number of 

 nuclei, and therefore corresponds to a considerable complex 

 of nerve cells. The mitotic figures found in olfactory fibres 

 of the rabbit show that the bipolar cells of the olfactory 

 nerve do not grow into the bulbus, but extend in length in 

 such a way that with the increased length of the fibre the 

 nuclei multiply, so that finally there results a peculiar long, 

 multi -nucleate nerve cell, which can only be compared with 

 the sympathic. 



