144
=
THE ,BIOLOGY OF FÏSHES
be, that the inuence of the hormones
over
a.
'
_
' _
longer period of time.
_
Very little is known regarding the origin and activities
]
of these substances in shes, but it may be assumed that
their function is similar to that in higher animals; The
spleen (sp, Fig. 31) lies alongside the stomaCh in close
connection frequently with the pancreas. In addition to
_
its inuence on the latter, it is an important centre forthe
‘
old red blood corpuscles and formation of
,
leucocytes, though this may be part of its business as
'
'
secretion—former.
’
_
_
The pancreas is in reality a composite gland, one part
pouring its secretions into the duodenum, the other part
'
_
enclos“ed within itself anddelivering its secretion only to.
‘
-
the; 1y_fphqàd blood
in_ its Substance.
The
,
detäched groups of cells
,
*
islets,’_’__èthe présence of Which in shes was determined
’
.
by ,Rennie
They
_
:
within recent years by the
“f
obtained from them, insulin,‘ is a palliatiVe fofd1abeteslt
the amount of sugar formed in the
under
'
normal conditions and has the effect, when introduced into
the blood of patients, of diminishing the excessive amounts
,j
of sugar which would otherwise overburden the kidneys.
'
'
T hethyroid and thymus glands arise in Connection with
the
gillearches, the former below, the—flatter
j
*
Originally, they
part onthe
_
j
»
protection
:
-
,
the
'
into the dermis,
.
l
“Ofïÿïnphoid Organ8- 'The thymus;
;
‘
like
to bean organ for the
,
_
of the red blood Corpusëzles,
but it‘may be
iS»part of the pto'cess of Secretion,
,
An’interesting thing is; that these“ glands seem to
in s0me ways‘z— Gudérnatchaÿ(rgj'1{)_
”
found thatthe metabolism and
—
Weregaccelerated bythyroid extract, but