1908. | Minute Structure of the Nervous System. 417 
of his great work, “Sulla Fina Anatomia degli Organi Centrali del Sistema 
Nervoso,” men of science were surprised at this invention and its results. 
Now, von Kolliker, myself, and others repeated this method, but, though 
we carefully followed Golgi’s directions, the results were not really satis- 
factory. 
Ithen began working by the new method of P. Ehrlich, which he published 
in 1886, and which consisted in staining living nerve tissue methylene blue. 
Golgi’s chrome-silver method had, however, in the inventor’s own hands, 
yielded a series of fundamentally important results, which are already 
mentioned in the Croonian Lecture of Cajal. Of these the following may 
be specially mentioned here also. The occurrence in the central organ of 
two types of nerve cells, those whose axis-cylinder process does not branch 
and come to an end until after a long course, and those whose processes, after 
a short course, branch copiously, and come to an end in the central organ ; 
further, the discovery of fine collateral branches emerging out of the axis- 
cylinder processes in the central organs; a more exact knowledge of the 
forms of the cells in the cortex of the cerebrum and the cerebellum, and 
more especially also in the gyrus hippocampi; the investigation of the 
different types and methods of ramification of the dendrites, and an enquiry 
into the structure of bulbi olfactorii. Golgi had become convinced that in 
the grey substance of the spinal cord there exists an exceedingly extensive 
and delicate network, which he considered was due to anastomosing of the 
collateral branches, and not, as Gerlach before supposed, to the anastomosing 
of the dendrites. 
During the next following years, however, Golgi’s method did not yield 
any very remarkable results; the scientists who used it did not obtain any 
real success with it. 
Ehrlich’s methylene method, on the other hand, was tried and valued in 
some places, especially in Kazan by Arnstein, Dogiel, and Smirnow, and in 
Stockholm by myself. In the higher animals, the vertebrata, the method 
could be well applied to the peripheral nervous system, but to the central 
one only with the utmost difficulty. I then determined to try and find some 
lower animals which admitted of having their whole nervous system, or, at any 
rate, the principal parts of it stained, so that by experimenting with them one 
might obtain a comprehensive idea of their entire construction. At last, in 1890, 
I found, with a certain modification, that the method gave excellent pictures 
in the ganglions of the ordinary crawfish (Astacus). A general survey was 
obtianed of their construction. One could clearly perceive that their 
so-called “ Punktsubstanz” of Leydig was formed of the lateral twigs of the 
processes of the unipolar nerve-cells, which twigs could be traced in the 
