6. Study the transfer of energy from the body to surrounding objects, as in moving substances and lifting weights.
Fill a half gallon jar two thirds full of water and carefully take the temperature with a chemical thermometer. Hold the hand in the water for four or five minutes and take the temperature again. Inference.
CHAPTER XIII - GLANDS AND THE WORK OF EXCRETION
In our study so far we have been concerned mainly with the introduction of materials into the body. We are now to consider the removal of materials from the body. The structures most directly concerned in this work are known as
Glands.—As generally understood, glands are organs that prepare special liquids in the body and pour them out upon free surfaces. These liquids, known as secretions, are used for protecting exposed parts, lubricating surfaces that rub against each other, digesting food, and for other purposes. They differ widely in properties as well as in function, but are all alike in being composed chiefly of water. The water, in addition to being necessary to the work of particular fluids, serves in all cases as a carrier of solid substances which are dissolved in it.
General Structure of Glands.—While the various glands differ greatly in size, form, and purpose, they present striking similarities in structure. All glands contain the following parts:
1. Gland, or secreting, cells. These are specialized cells for the work of secretion and are the active agents in the work of the gland. They are usually cubical in shape.
2. A basement membrane. This is a thin, connective tissue support upon which the secreting cells rest.