420 Prof. G. Retzius. Principles of the [June 15, 
Now, in the years 1891 and 1892, the renowned Hungarian histologist 
Michael von Lenhossék, applying successfully the Golgi method in the 
common earth-worm, Lumbricus, discovered that the epithelium cells in the 
epidermis send fine fibres to the ganglions of the central nervous system, 
where they divide and terminate with free endings. These cells showed 
themselves very clearly to be a kind of sensory peripheral nerve-cells, which 
are in contact with the elements of the nervous central organ, and are 
capable of conveying to them impressions from the periphery of the body. 
This discovery of von Lenhossék was shortly after confirmed by myself and 
developed in conjunction with a closer investigation of the structure of the 
ganglions (figs. 3 and 4). I showed, by means of the methylene and chrome- 
silver methods, that similar cells exist in the epidermis of polychets and 
molluscs, and-also in the crustacea, though the cell body in these animals 
lies lower down under the epidermis (figs. 5 and 6). 
Besides these sensory cells there exist also in the epidermis and the other 
epithelial tissues ‘ramifications of free endings of tactile nerves, whose cells 
are to be found deeper. 
I have mentioned these investigations in connection, particularly as they 
have for the most part been carried out by the methylene method. Now, 
however, a new era had commenced for Golgi’s chrome-silver method, as 
applied to the central nervous system of the higher animals. 
In and after 1888 Ramon Cajal, the great Spanish neurologist, published a 
series of works on the minute structure of the brain and spinal cord of 
vertebrate animals. By means of Golgi’s method, which he improved and 
used in a masterly manner, Cajal succeeded in investigating the forms and 
the distribution of the nerve-cells and their processes in the different parts 
of the central nervous organ. We may date from this time almost a new 
epoch in our knowledge of the minute structure of the nervous system. 
Cajal’s first discoveries had an electrifying effect upon those who were 
working in the same field. For my part I shall never forget the overwhelming 
impression that the demonstration by Cajal, at the Berlin Anatomical 
Congress of 1889, of a large series of his preparations produced upon those 
of us who were specially interested in the subject. Albert von Kolliker and 
I were enchanted by the sight of the preparations which Cajal placed before us. 
Both he and I were converted, and we started home to begin working afresh 
with Golgi’s method, which was not in great repute among other anatomists 
of that day. Kdlliker, as well as von Lenhossék, working then in Kolliker’s 
laboratory as his prosector, succeeded in applying Golgi’s method, and 
published several excellent new researches. At the same time I, in Stockholm, 
and Van Gehuchten, in Louvain, were applying the same method, while 
