The appendages of the skin are the nails, the hairs, the sudoriferous and sebaceous glands, and their ducts. The nails and hairs are peculiar modifications of the epidermis, consisting essentially of the same cellular structure as that membrane.
The general framework of the body is built up mainly of a series of bones, supplemented, however, in certain regions by pieces of cartilage; the bony part of the framework constitutes the skeleton.
Fracture of the patella may be produced by muscular action or by direct violence. When produced by muscular action, it occurs thus: a person in danger of falling forwards attempts to recover himself by throwing the body backwards, and the violent action of the quadriceps extensor upon the patella snaps the bone transversely across.
I have removed the spleen from a dog, from cats, and rabbits. In all cases, the animals survived the operation and did not appear to be in the least affected by the absence of the organ.
The earliest period at which I have been able to detect the existence of the spleen in the human embryo is at the second month.
Bone is one of the hardest structures of the animal body; it possesses also a certain degree of toughness and elasticity.
