Adipose Tissue consists of an aggregation of minute spherical pouches or vesicles filled with fat or oil. Under the microscope, each vesicle presents a very delicate envelope inclosing a drop of the oily matter. Thus it is that in the living body the fat, although nearly liquid, is not moved by gravitation, as is the case when the filamentous tissues are infiltrated by the water of dropsy. It is copiously supplied with capillary blood-vessels, but no nerves have been seen to end in it, and thus it may be punctured without causing pain. Adipose tissue is widely distributed throughout the body. It occurs as the yellow marrow of bones. A considerable layer is found under the skin, where it serves to give smoothness and roundness to the contour, and, being a bad conductor of heat, it is specially valuable in retaining the warmth of the bodies of animals exposed to great cold, such as whales. Being light and elastic, it forms an excellent packing substance; hence it is found surrounding large vessels and nerves, in the omentum and mesentery, round the kidneys, joints, &c., where it affords support, and protects from injurious pressure. Its utilisation as a reserve supply of nutriment is well illustrated in hibernating animals like the hedgehog.
