LAMENESS: ITS CAUSES AND TREATMENT. 301 
greatly in shape and size, being flat, triangular, long, short, or broad, 
and are variously and capriciously named, some from their shape, 
some from their situation, others from their use; and thus we have 
abductors and adductors—the pyramidal, orbicular, the digastricus, 
the vastus, and soon. Those which are under the control of the will, 
known as the voluntary muscles, appear in the form of fleshy struc- 
tures, red in color, and with fibers of various degrees of fineness, 
and are composed of fasciculi, or bundles of fibers, united by con- 
nective or cellular tissue, each fasciculus being composed of smaller 
ones but united in a similar manner to compose the larger forma- 
tions, each of which is enveloped by a structure of similar nature 
known as the sarcolemma. Many of the muscles are united to the 
bones by the direct contact of their fleshy fibers, but in other 
instances the body of the muscle is more or less gradually trans- 
formed into a cordy or membranous structure known as the tendon 
or sinew, and the attachment is made by the very short fibrous 
threads through the medium of a long tendinous band, which, pass- 
ing from a single one to several others of the bones, effects its object 
at a point far distant from its original attachment. In thus carrying 
its action from one bone to another, or from one region of a limb to 
another, these tendons must necessarily have smooth surfaces over 
which to glide, either upon the bones themselves or formed at their 
articulations, and this need is supplied by the secretion of the syno- 
vial fluid, a yellowish, unctuous substance, furnished by a peculiar 
tendinous synovial sac designed for the purpose. ‘ 
Tllustrations in point of the agency of the synovial fluid in assist- 
ing the sliding movements of the tendons may be found under their 
various forms at the shoulder joint, at the upper part of the bone of 
the arm, at the posterior part of the knee joint, and also at the fet- 
locks, on their posterior part. 
As the tendons, whether singly or in company with others, pass 
over these natural pulleys they are retained in place by strong, © 
fibrous bands or sheaths, which are by no means exempt from danger 
of injury, as will be readily inferred from a consideration of their 
important special use as supports and reenforcements of the tendons 
themselves, with which they must necessarily share the stress of 
whatever force or strain is brought to bear upon both or either. 
We have referred to that special formation of the external surface 
of a bone by which it is adapted to form a joint or articulation, 
either movable or fixed, and a concise examination of the formation 
and structure of the movable articulations will here be in place. 
These are formed generally by the extremities of the long bones, or 
may exist on the surfaces of the short ones. The points or regions 
where the contact occurs are denominated the articular surface,which 
assumes from this circumstance a considerable variety of aspect and 
