It is probable, therefore, that the supra-renal bodies maintain in circulation in the blood minute quantities of some active substance which helps to maintain the tone of the volun tary muscles of the body, as well as the tone of the involuntary muscle of heart and blood vessels.
The Pituitary and Pineal Glands are small bodies situated towards the base of the brain. The pituitary body is called from pituita, Latin for phlegm, because it was supposed by the ancients to discharge phlegm or mucus down the nostrils. The pineal gland is a small body about the size of a cherry stone, and is called from pinea, a pine. It is placed in front of the corpora quadrigemina (p. 134). Both of them are formed of epithelial cells.
Of the pituitary body it may be said that it seems to be associated in function with the thyroid gland. Results such as attend destruc tion of the thyroid follow destruction of the pituitary body. A very peculiar disease, called acromegaly, attended by great enlargement of the hands and feet, and changes in the bones of spine and face, has been shown to be associated with degeneration of the pituitary body, and feeding with the pituitary of ani mals has been tried as a form of treatment for this disease. It has been supposed also that
degeneration of the thyroid may be to some degree compensated by enlargement of the pituitary. In any case it also appears to pro duce an internal secretion whose effect upon the blood affects the nutrition of the tissues, and specially of the heart, vessels, and nervous system.
The pineal gland, to call it also a gland, is more likely to be merely a vestigial structure, a remnant of a stage of development of the body.
Payer's Glands have been already men tioned as occurring in the mucous membrane of the intestine, sometimes singly, sometimes in groups (p. 199). They are small, round, shut sacs, composed of a fibrous tissue capsule, and containing the same sort of tissue as the lymphatic gland. They are affected in typhoid fever. Because of their resemblance in struc ture, they are classed with the blood glands, nothing being known of their functions.