SECTIONAL TRANSACTIONS.—I. 433 
is a whirlpool movement in the centre of the field of vision. With spectral 
colours projected on a screen in a dark room, the positive after-image of all 
becomes purple and disappears without changing to negative when viewed 
for the shortest possible time. When the eye is moved the after-image 
spreads out, a portion of the retina not previously stimulated being affected. 
These facts prove conclusively that the photo-chemical stimulus in vision 
is liquid and movable in the retina. 
Monday, September 9. 
PRESIDENTIAL Appress by Prof. P. 'T. HERRING on The pituitary body and 
the diencephalon (10.0). (See p. 143.) 
Dr. J. Beatt1eE.— The relation of the pituitary to the hypothalamus (11.0). 
The posterior lobe of the pituitary gland is connected to the hypo- 
thalamus by nervous and chemical links. Nerve fibres from the pre-optic 
area of the hypothalamus make their way into the pituitary stalk and end in 
the posterior and intermediate lobes. The existing evidence favours the 
secretory nature of the fibres. No fibres are known which pass into the 
anterior lobe from the hypothalamus. Chemical links between the posterior 
lobe and the hypothalamus have been denied, but the weight of evidence for 
posterior lobe hormones is in favour of the presence of at least some hor- 
mones in the intact animal. The cells from which these hormones are 
elaborated and the method of their transference to their places of action 
are not yet proved. The various theories are discussed. The relation of 
the pituitary and the hypothalamus to problems of water, fat, and carbo- 
hydrate metabolism throw much light on the neurohormonal control of the 
autonomic nervous system and on the place of the hypothalamus in the 
animal economy. 
Dr. A. S. Parkes, F.R.S.—Relation of the pituitary to reproduction (11.20). 
Dr. J. M. Peterson.—The relationship of the pituitary gland to carbohydrate 
metabolism (11.40). 
Observations by Houssay, Cushing and others have clearly demonstrated 
that the symptoms of diabetes may be controlled by the agency of the anterior 
lobe of the pituitary gland. Implantation of this lobe, or injection of an 
extract from it, has a diabetogenic effect, while excision of the gland alleviates 
the symptoms of diabetes. 
The diabetogenic substance has been shown to act without the mediation 
of the pancreatic islets, thyroid, or the adrenal medulla; evidence with 
regard to the possible mediation of the adrenal cortex is as yet scanty. 
The postulate that it acts on nerve centres, which control carbohydrate 
metabolism through the autonomic nervous system, is interesting in 
view of the recent observations with regard to the relationship of the 
hypothalamus and the pons to the blood sugar level. The evidence for 
such a mechanism is, however, inconclusive. 
It is claimed that the diabetogenic extract is divisible into ketogenic and 
blood-sugar-raising fractions, and has not been identified with any other 
known physiological agent extractable from the pituitary gland. 
The rise in blood lactic acid which follows intravenous injection of the 
pressor substance of the posterior lobe is attributable to a diminution in 
transference of oxygen from blood to tissues (Geiling and others). 
