a telescope.

APEX, the Latin word (pl. _apices_) for the top, tip or peak of
anything. A diminutive "apiculus" is used in botany.

APHANITE, a name given (from the Gr. [Greek: aphanes], invisible) to
certain dark-coloured igneous rocks which are so fine-grained that their
component minerals are not detected by the unaided eye. They consist
essentially of plagioclase felspar, with hornblende or augite, and may
contain also biotite, quartz and a limited amount of orthoclase.
Although a few authorities still recognize the aphanites as a distinct
class, most systematic petrologists, at the present time, have discarded
it, and regard these rocks as merely structural facies of other species.
Those which contain hornblende are uniform, fine-grained diorites,
vogesites, &c., while when pyroxene predominates they are ascribed to
the dolerites, quartz-dolerites, &c. Hence, any rock which is compact,
crystalline and fine grained, is frequently said to be _aphanitic_,
without implying exactly to which of the principal rock groups it really
belongs.

APHASIA[1] (from Gr. [Greek: a], privative, and [Greek: phasis],
speech), a term which means literally inability to speak, and is used to
denote various defects in the comprehension and expression of both
spoken and written language which result from lesions of the brain.
Aphasic disorders may be classed in two groups:--first, receptive or
sensory aphasia, which comprises (a) inability to understand spoken
language (auditory aphasia), and (b) inability to read (visual aphasia,
or _alexia_); second, emissive or motor aphasia, under which category
are included (a) inability to speak (motor vocal aphasia, or _aphemia_),
and (b) inability to write (motor graphic aphasia, or _agraphia_). It
has been shown that each of these defects is produced by destruction of
a special region of the cortex of the brain. These regions, which are
termed the speech centres, are, in right-handed people, situated in the
left cerebral hemisphere; this is the reason why aphasia is so commonly
associated with paralysis of the right side of the body.

A study of the acquisition of the faculty of speech throws light upon
the education of the speech centres, and helps to elucidate their
physiological interaction and the phenomena of aphasia. The auditory
speech centre is the first to show signs of functional activity, for
within a few months of birth the child begins to _understand_ spoken
lan