3 ° 
Sir Everard Home on the 
the part is not sufficiently soaked in water, they cannot be 
separated ; and if macerated too much, the whole is dissolved 
into a mass, like cream. The corpus callosum resembles the 
medulla spinalis, but contains a greater quantity of globules 
~oo °f an inch than any other part of the brain; the 
quantity of mucus and fluid are at least equal to the globular 
tissue. 
Every part of the substance of the brain is pervaded by 
innumerable blood vessels, which are of considerable size 
towards the centre, but branch out to an extreme degree of 
minuteness, less than the half diameter of a red globule with 
its colouring matter ; and even when of that size the fluid 
they carry is red, as in PL II. fig. 4. 
These arteries in the brain never anastomose, as in the reti- 
na ; their branches are accompanied by veins of still less 
diameter, having valves. The valves are at very short dis- 
tances, particularly near their extremities ; and when the 
brain is fresh, these veins contain a red fluid. See Fig. 3. 
The circumstances noticed by Mr. Bauer, namely, the cor- 
tical substance of the cerebrum and cerebellum being made up 
of the small globules; containing the gelatinous fluid soluble 
in water in great abundance ; and having branches more 
minute than the other arteries of the brain ; also the cor- 
responding veins having valves similar to those found in 
absorbent ves sel and their canals carrying a red fluid, — 
throw' considerable light upon the functions of the brain, 
and show that the cortical substance is one of the most 
essential parts of this organ, although the pons verolii, as 
the commune vinculum between the different portions of this 
complicated structure, may be the most essential to life. 
