84 The Neuroglia of the Spinal Cord of the Elephant 
Although neuroglia was discovered by Keuffel in 1811, the distinctive 
nature of the tissue was not considered until 1846 when Virchow de- 
scribed it under the name it now bears. The study of neuroglia, how- 
ever, did not really begin till the advent of the silver method of Golgi. 
This method, though described by its inventor as early as 1873, re- 
mained practically unnoticed and unused till after 1885, when Golgi’s 
more voluminous work appeared. ‘This method not only was the means 
of certain important additions to our knowledge of the development of 
the tissue, but also through it the fibrous nature of neuroglia was estab- 
lished. Previous to 1895, however, our knowledge of neuroglia as a 
tissue consisted almost entirely of what could be shown by the precipi- 
tation of the silver salt. The investigators, chief among whom were 
Golgi himself, Kolliker, Cajal, Ranvier and Lenhoss¢k, had no means of 
confirming their observations by adequate control methods and, as the 
natural consequence of a precipitative method, the later daylight upon 
its results has shown that certain of their conclusions were erroneous. 
The appearance of Weigert’s paper in 1895, giving the results of a new 
method he had devised, marked the beginning of a new epoch in the 
study of neuroglia. Since Weigert’s publication no less than twenty- 
three papers have appeared giving results obtained either by the applica- 
tion of his method or of others newly devised. Most of these papers 
do little more than confirm Weigert’s results. While certain of them 
add a few details to the knowledge of the tissue, on the whole they 
have strengthened rather than detracted from Weigert’s original con- 
clusions. The more important of these papers and the literature on 
the subject in general, have been repeatedly reviewed and so thoroughly 
by Aguerre* and Reinke‘ and more recently by Huber, that it is 
considered unnecessary to attempt here anything like a detailed review 
of the literature. The more important and commonly accepted state- 
ments may be summated as follows: 
1. Structurally, neuroglia as a tissue consists of neuroglia cells and 
neurogha fibers. 
2. The neuroglia cells vary in size and shape. They usually possess 
branched cytoplasmic processes. The cytoplasm, however, is present in 
varying amounts, many of the cells having but a small quantity which 
closely invests the nucleus or sometimes occurs only on one side of it. 
Most of the neuroglia nuclei are described as free from cytoplasm. 
The nuclei are of the vesicular type but vary greatly in shape and size. 
6Aguerre. Archiv f. Mikros. Anat., Vol. LVI, 1900. 
7Reinke. Archiv f. Mikros. Anat., Vol. L, 1897. 
SHuber. Loe. cit. 
