that particular region with blood. The cause of the blocking of the two
arteries was discovered, for little warty vegetations were found on the
mitral valve of the left side of the heart. I interpreted the two
attacks thus: one of these warty vegetations had become detached, and
escaping into the arterial circulation, entered the left carotid artery
and eventually stuck in the posterior branch of the middle cerebral
artery, causing a temporary loss of word memory, consequently a
disturbance of the whole speech zone of the left hemisphere. This would
account for the deafness to spoken language and loss of speech for a
fortnight, with impairment for more than a month, following the first
attack. But both ears are represented in each half of the brain; that is
to say, sound vibrations entering either ear, although they produce
vibrations only in one auditory nerve, nevertheless proceed subsequently
to both auditory centres. The path most open, however, for transmission
is to the opposite hemisphere; thus the right hemisphere receives most
vibrations from the left ear and _vice versa_. Consequently the auditory
centre in the right hemisphere was able very soon to take on the
function of associating verbal sounds with the sense of movement of
articulate speech and recovery took place. _But
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