Because the motions of the hands and feet are very _varied and complicated_. There are no less than _twenty-eight bones_ in one hand and wrist; and about _as many_ in a foot and ankle. To these are fastened a great number of _ligaments and muscles_, by which their varied compound movements are controlled. But for the complexity of the mechanism of our hands and feet, our motions would be extremely awkward, and many of the valuable mechanical inventions which now benefit mankind, could never have been introduced. The bones of the hands and feet are in number equal to _one-half of the whole of the bones of the body_. CHAPTER XLVI. 937. _What are ligaments?_ Ligaments consist of bands and cords of a _tough_, _fibrous_, _and smooth substance_, by which the bones are bound together and held in their places, allowing them freedom to move, and supplying smooth surfaces over which they glide. 938. _Why are the joints bound with ligaments?_ Because the bones would otherwise be constantly liable to _slip from their places_. [Verse: "That which is born of the flesh is flesh; and that which is born of the Spirit is spirit."--JOHN III.] 939. _What are tendons?_ Tendons are _long cords_, of a substance similar in its nature to _cartilage_, by which _the muscles are attached to the bones_. [Illustration: Fig. 56.--SHOWING A BALL AND SOCKET JOINT, AND THE MANNER IN WHICH LIGAMENTS ARE EMPLOYED TO HOLD BONES IN THEIR POSITIONS.] A. The _ball_, or _head_ of the thigh bone. B. The _socket_, showing the ligament in the socket, which holds the head of the bone in its place, but allows it free motion. C. _Ligaments_ tied from bone to bone, giving firmness to the parts. 940. _Why are tendons used to attach the muscles to the bones?_ Because, by this arrangement, the large muscles by which the extremities are moved, _may be placed at some distance_ from the bones upon which they act, and thus the extremities, instead of being large and clumsy, are _small_ and _neat_. 941. _How many muscles are there in the human body?_ There are about _four hundred and forty-six muscles_ that have been dissected and described, and the actions of which are perfectly understood. But there is probably a much larger number of muscles, and of compound actions of muscles, than the skill of man has been able to recognise. [Verse: "All flesh is not the same flesh: but there is one kind of flesh of men, another flesh of beasts, another of fishes, and another of birds."--CORINTHIANS XVI.] [Illustration: Fig. 57.--ILLUSTRATION OF THE RELATION OF MUSCLES, TENDONS, AND BONES.] 942. _What is the constitution of a muscle?_ Every muscle is made up of a number of _parallel fleshy fibres_, or threads, which are bound together by a smooth and soft tissue, forming a sheath or case to the muscle, and enabling it to _glide freely_ over the surfaces upon which it moves.