THE BRAIN. 
67 
But besides these there are other actions which can 
only be attributed to a certain degree of intelligence. 
We will now examine that part which Dujardin 
(33), Brandt (10), and others describe as the seat of 
intelligence, the supra-oesophageal ganglion, or brain. 
Fig. 29, a, shows the brain in its relation to the 
ganglionic chain, and Figs. 31 and 32 enlarged views 
of the brain deprived of its outer coverings, as given 
by Dujardin in his memoir. He says the brain 
is so soft and transparent that it is not possible to 
recognise its structure or trace its form without first 
Fig- 31. — Brain Deprived of Fig. 32. — View from Top 
Outer Covering. of Fig. 31. 
hardening it with alcohol or turpentine, as was done 
by Swammerdam. But it is necessary to examine 
the brain in a fresh state to recognise the character of 
its substance, and that of the coverings which envelop 
it. When the cranium is removed, we only sec first the 
adipose tissue, the salivary glands, numerous tracheae, 
and tracheal sacs, which completely hide the brain. 
If these are removed, it will be seen that the trachean 
sac is attached to the brain, which it surrounds 
