REGULATORS 595 



may be replaced by a dilatation and fall of pressure. In birds 

 the first dose produces this dilator effect. In the renal 

 arterioles it causes a dilatation, and in the coronary arteries a 

 constriction, thus differing from adrenalin. 



(2) On the heart it acts to increase the force of contraction, 

 whether the vasfus is intact or is cut. After section of the 

 vagus it does not accelerate the heart as does adrenalin. 



(3) Upon the iris it acts like adrenalin. 



(4) On the intestine, uterus, and bladder it acts as an 

 excitant, and it also increases the effect of stimulating the 

 hypogastric nerves on the last two organs. 



(5) It causes a great outpouring of milk from the 

 mammary glands, probably by its action on the walls of the 

 ducts, but it has no influence on milk secretion. 



(6) It has a marked diuretic action, and, since this occurs 

 even after a second dose when the arterial blood pressure 

 falls, it has been ascribed to a specific stimulating action on 

 the secreting cells of the kidney. 



(7) Its action on metabolism requires further investigation. 

 According to some investigators, it causes glycosuria. 



So far the chemical nature of the active principles, which 

 may be called Hypophysin, has not been ascertained, although 

 active crystalline products have been prepared Like adrenalin, 

 it is not destroyed by heating. Whether it is a normal product, 

 and whether it has any physiological significance, has yet to be 

 proved. Herring's results seem to show that the passage of a 

 colloidal material may be traced into the ;erebro-spinal fluid. 

 It is entirely formed in the hypophysis or \u the pars intermedia 

 of the pituitary. Some observations by Herring tend to show 

 that the action on milk flow and on the uterus is more particu- 

 larly due to a product of the latter. 



II. From the Buccal Cavity. 

 3. Thyreoid Gland. 

 1. Development. — This structure is formed as a hollow out- 

 growth from the anterior part of the alimentary canal, which 

 breaks up into numerous branches. 



^ The gland was named after the shield-like cartilage of the larynx. Since 

 dvpeos is a shield, and dvpos a door, it should be called thyreoid. The name 

 thyroid given by British anatomists is manifestly erroneous. 



