9 
internal structure of the human brain , &c. 
Fig. 7. The cavity in the tench's brain. 
Fig. 8. The brain and nerves of the humble bee ; magnified 
ten diameters. 
The brain is of a truncated oval form ; it gives off the 
nerves to the eyes and feelers ; its internal structure made 
up of globules. The substance, corresponding in its uses to 
that of the medulla spinalis, is nodulated on its external sur- 
face, connected to the brain by two long chords, which differ 
from nerves in collapsing soon after being exposed ; these I 
shall call crura cerebri : the lower portion of this nodulated 
structure corresponds to the medulla spinalis, and, in its in- 
ternal structure, resembles the brain. 
The two nerves that go down, connected at certain dis- 
tances by small nodules, are different from nerves in being 
more pulpy, and the nodules themselves are composed of 
congeries of nerves, similar to the ganglions in the human 
body, of which there are many excellent representations be- 
fore the public, which makes it unnecessary to show their 
structure upon this occasion. 
Fig. 9. The brain and nerves of the garden snail ; mag- 
nified four diameters. 
In this animal the brain is made up of two apparently equal 
portions. As the appearance at the termination of the two 
large horns resembles eyes, and Swammerdam has attempted 
to delineate the different parts of the organs : Mr. Bauer has 
shown the two nerves in different states. 
The medulla spinalis forms a larger mass than the brain, 
but equally made up of two distinct parts. From the upper 
edge of this mass, there is an azagos branch going directly 
MDCCCXXIV. C 
