1898-99. | STRUCTURE, MICRO-CHEMISTRY AND DEVELOPMENT OF NERVE CELLS. 407 
The mode of occurrence of these granules in embryonic and foetal 
cells has evoked considerable interest. Vas* and Eve found the chromo- 
philous substance uniformly distributed in the nerve cells of fcetal 
rabbits, and Szczawinska’ observed the same for embryonic cells of 
selachians. Biihler noticed that the granules were entirely absent from 
the nerve cells at an early stage. Timofeew” observed that in the inter- 
val between the fourth and sixth day of incubation in the chick, the 
chromophilous substance increased markedly in amount and was uni- 
formly distributed. 
None of the above observers seem to have suspected any other than a 
cytoplasmic origin for this substance and none of them have followed 
out in detail the appearance of this substance in the cell. The nucleo- 
proteid nature of these bodies suggested the nucleus as a possible source 
of the substance forming them, and this inference has been confirmed 
by a series of observations made on mammalian and avian embryos, 
Further evidence in support of the nuclear origin of these bodies is found 
by the examination of the structure of the nerve cells of animals in which 
‘no Nissl granules occur. These observations will form Parts 2 and 3 of 
the present memoir, while Part 4 will be devoted to the discussion of 
certain general considerations with respect to the structure of the nerve 
cell that have recently been the subject of much investigation: 
The question of a good fixing agent for nerve cells has been discussed 
by many writers but more particularly by Flemming," v. Lenhossek” and 
Held.’ Flemming, v. Lenhossek and with them many others find that 
saturated aqueous sublimate is the most satisfactory fixing fluid for nerve 
cells. Held, believing in the foam-like structure of protoplasm, does not 
consider it as good as other fluids. Besides sublimate, Carnoy’s fluid, 
Flemming’s fluid and picrosulphuric acid are generally found to give good 
results. With all these fluids fair results were produced, but the sharpest 
granules and the clearest intergranular substance were obtained by using 
the modification of Foa’s fluid as recommended by Bensley," viz., equal 
8 Vas, Friedrich, ‘Studien tiber den Bau des Chromatin in der -‘Sympathischen Ganglienzelle,” Arch. 
f, Mik. Anat., XL, p. 375, 1892. 
9 Szezawinska, W., ‘‘Recherches sur le systeme nerveux des Selaciens,” Arch. de Biologie, XV, Pp: 
463, 1897. 
10 Timofeew, D., “ Beobachtungen iiber den Bau der Nervenzellen des Spinalganglien und des Sym- 
patheticus beim Vogel,” Inter. Monat. f. Anat. u. Physiol, XV, p. 259, 1898. 
11 Flemming, W., ‘*Ueber den Bau der Spinalganglienzellen bei Saugethieren, und Bemerkungen iiber 
den der centralen Zellen.” Arch. f. Mik. Anat,, XLVI, p. 379, 1895. 
12 v. Lenhossek, M., ‘*‘ Ueber den Bau der Spinalganglienzellen des Menschen,"’ Arch. f. Psychiatrie, 
XXIX, p, 345, 1897. 
13 Held, H., 1. c. and Arch. f; Anat. u. Phys., Supp., p. 273, 1897. 
14 Bensley, R. R., ‘*Mammalian Gastric Glands,” Proceedings of Canadian Institute, Vol. I, Part 1, 
p. x1, 1897. 
