I—PHYSIOLOGY 155 
Houssay and Biasotti consider that the pituitary as a whole is active in 
metabolism, but that the anterior lobe is the more important. Harvey 
Cushing looks to a nervous control in the hypothalamus, in which pituitary 
and nervous mechanisms work together in the regulation of the metabolism 
of solids as they do in the case of water. Hunger and thirst are sensations 
of primary importance to the animal. The nerve impulses responsible 
for their production act on the diencephalic mechanism, and the pituitary 
body is called upon to make the necessary adjustments. 
The action of pituitrin as a stimulant of uterine muscle was discovered 
by Dale in 1906. ‘The hormone, now known as oxytocin, is a product 
of the pars intermedia, though stored in greater abundance in the pars 
nervosa. It is held by some to be an important element in the termination 
of pregnancy. ‘The active principle is not confined to the mammalian 
pituitary, and it is said to be present in the Ascidian ‘ pituitary.’ This 
fact alone points to a wider application of the hormone. 
Ott and Scott in 1910 described the galactogogue effect of posterior lobe 
extracts. The material responsible can be formed by cells other than those 
of the posterior lobe, for it is present in the elasmobranch pituitary and 
must therefore have an epithelial origin. 
The action of pituitrin upon melanophores has been described by 
Hogben and Winton and others. It is interesting to note that the ex- 
pansion of the melanophores brought about by pituitrin is the reverse of 
that produced in tadpoles by extracts of the pineal body. 
Zondek and Krohn have recently claimed the presence of a specific 
hormone, ‘ intermedin’ which gives a characteristic erythrophore effect 
in the minnow. The hormone is said to be formed by the cells of the 
pars intermedia and liberated into the third ventricle. Traces of it may 
be found in the wall of the ventricle, but not in the blood or in the fourth 
ventricle. Its action is presumably upon a local nerve mechanism in the 
diencephalon, and is said to be specific. 
Other activities of the posterior lobe have been described. Dodds and 
Noble have advanced the theory that the control of blood destruction is 
exercised by the posterior lobe through an influence upon reticulo- 
endothelium. ‘They have obtained by the injection of extracts in rabbits 
hemorrhagic lesions of the acid-secreting areas of the stomach, and rapid 
destruction of red blood corpuscles accompanied by an increase of 
macrocytes. 
Other effects upon the blood are described. ‘The production of ulcers 
in the stomach and upper parts of the intestine has been attributed to 
the action of pituitrin upon nervous mechanisms in the hypothalamus 
controlling the blood vessels of these areas. 
A multiplicity of actions can undoubtedly be evoked by extracts of the 
posterior lobe, but one may well question if all be normal functions. 
The oxytocic principle is found in male as well as in female animals, 
and there is a remarkable similarity in many of the products of the 
pituitaries of all vertebrates, irrespective of their apparent physiological 
requirements. One is compelled to conclude that the active principles 
of the pituitary are such as are necessary for the regulation of common 
and fundamental processes in the life of the animal. 
