426 Prof. G. Retzius. Principles of the [June 15, 
in the grey substance (Punktsubstanz) of the invertebrata, but only a twist- 
work, a plexus, of delicate branches of nerve-cell processes, intricately 
intertwined. 
So we were all prepared, in accord with Cajal’s definite pronouncement, to 
regard the connection between the various nerve-cells and their processes as 
effected, not by continuity but by contact. 
In his excellent and concise review of the investigations in this depart- 
ment during the previous years, Waldeyer, in 1891, called this conception of 
a nerve-cell as an independent unit a neurone, a term which has since been 
generally adopted to imply the independence of the nerve-cells. 
This doctrine, the newrone theory, as enunciated by Waldeyer, appeared to 
gain more and more ground in neurology. His’, Cajal’s, v. Kolliker’s, 
v. Lenhossék’s, Van Gehuchten’s, and my own investigations had given the 
basis to and had confirmed this theory in many directions. 
As for the retina, Dogiel described the nerve-cells as anastomosing, but 
Cajal’s investigations by the Golgian method gave, as to this point, quite 
different results from Dogiel’s. And as regards the peripheral nerve-ends 
I may say that, though I have carried out extensive researches upon them, 
I have never been really able clearly to see any formation of network, either 
among the terminal ramifications of the different neurones or in those of one 
and the same neurone. Thus, I have never been able to observe a reticulum 
between the terminal ramifications of a motor nerve-fibre on a muscle, nor 
in those of a sensitive nerve-fibre, nor on a nerve-fibre of one of the sensory 
organs. Supposing such a connection were really to occur, as it is described 
by some histologists, I must regard a reticulum of that kind as rather 
abnormal, due to some sort of secondary coalescence. I have considered 
myself bound to specially notify these facts, as they are of importance for 
the neurone theory as a whole. 
The question of the relation and connection of the peripheral sensory cells 
to the nerve-fibres is also of fundamental importance. Scientists have long 
assumed, and in some cases asserted that they had observed, that in the 
higher animals each of those cells was directly connected with a nerve-fibre. 
That was held to be the case with the organs of smell and taste, and also with 
regard to the organ of hearing. 
Now, how was this fact to be explained by the principles of the neurone 
theory? This question came forward: Can a nerve-fibre be directly 
connected with both a central and a peripheral cell, or be actually a process 
of both of them ? 
This important question, thanks to the researches of the last two decades, 
found a perfectly natural explanation and one that fits in with the neurone 
