XIV 
CONTRIBUTIONS TO THE BRAIN PHYSIOLOGY OF 
WORMS! 
I 
In his well-known work Ueber Entwicklungsgeschichte 
der Thiere K. E. von Baer asks how the anterior pair of 
ganglia of segmented animals should be designated. 
Whether the first pair of ganglia of the segmented animals shall 
be called a brain or not depends entirely upon the significance 
which the word brain is given. It is certainly not the organ which 
we call the brain in vertebrates, for in them it is the anterior 
extremity of the neural tube, and this is lacking in the segmented 
animals. It is rather the foremost pair of the series of ganglia, 
and as the latter is to be compared with the spinal ganglia of the 
vertebrates the so-called brain of the segmented animals seems to 
correspond to the Gasserian ganglion of the vertebrates,’ for the 
latter also receives sensory impulses. .... If, however, one wishes 
to designate by the term brain not a definite organ, but.... 
that mass of nervous tissue which receives the sensory impulses, 
then one can, of course, say that insects possess a brain. Only one 
must keep the meaning of this term in mind. 
He who seeks a definition for the word brain will find 
the necessary directions in von Baer’s remarks. Steiner® 
considers it the problem of the physiologist to find such a 
definition, and has come, apparently without knowledge of 
the remarks of von Baer, to a different definition which 
reads as follows: 
The brain is characterized by being the general center of loco- 
motion in connection with the activities of at least one of the 
higher sensory nerves. .... Besides its simplicity this definition 
1 Pfliigers Archiv, Vol. LVI (1894), p. 247. 
2Vol. I (1828), pp. 234 ff. 
3 Sitzungsberichte der Berliner Akademie der Wissenschaften, 1890. 
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