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Croontan LecturE.—The Principles of the Minute Structure of 
the Nervous System as revealed by Recent Investigations. 
By Professor GustaF Rerzius, For. Mem. RS. 
(Lecture delivered May 14,—MS. received June 15, 1908.) 
When the flattering invitation to deliver this year’s Croonian Lecture 
before your far-famed Royal Society reached me, I first of all felt con- 
siderable hesitation as to whether I should be able to discharge so honourable 
a task. 
The very choice, out of the field of my investigations, of a subject which 
should be suitable for lecturing to you about, presented a very real difficulty. 
During the past 20 years I have been working principally in three depart- 
ments of scientific research—the Nervous System of Vertebrata and 
Invertebrata, Physical Anthropology in Sweden, and the Spernia of Animals of 
all Orders. 
By far the most interesting of these subjects is the first, dealing as it does 
with the chief organ in nature, that of the psychical functions. Upon this 
subject, of the minute structure of the nervous system, there has been a 
great deal of light thrown during the last two decades by the histological 
researches of a number of scientists, of whom may be specially mentioned 
the eminent Italian and Spanish neurologists Camillo Golgi and Ramon 
Cajal. 
The subject, however, has two real drawbacks: on the one hand it is 
exceedingly complicated, especially as several of its results are still under 
debate; and on the other it has already, in 1894, been treated of in a 
Croonian Lecture by Professor Cajal. Since his lecture, however, 14 years 
ago, the discoveries made in this department of science have been very 
numerous, many of them due to the researches of Cajal himself. At last I 
came to the conclusion that I might on this occasion continue and bring up 
to date the review of the subject which he then gave you. 
In pursuing this intention I have, however, been obliged here and there to 
glance back at work done prior to 1894, and also to speak of some aspects of 
the subjects upon which my predecessor only touched very lightly. I conclude 
that it is in accordance with the idea of these lectures that the lecturer may 
also mention some of his own researches. And I hope that you will pardon 
me for expressing my opinion more definitely in certain particulars, seeing 
that I have arrived at a conviction of my own respecting them, which is 
, based upon investigations which I have myself carried out. I regard this as. 
