| Water, | 744 | .5 | ||||
| Solids. |  | Myosin and other matters, elastic elements, etc. | 155 | .4 | ||
| Soluble elements, | 19 | .3 | ||||
| Gelatine, | 20 | .7 | ||||
| Extractives, | 37 | .1 | ||||
| Fats, | 23 | .02 | 55 | .5 | ||
The muscles of the flesh form a large proportion of the weight of the whole body. Calculated for a man of 150 pounds’ weight:
| The skeleton, bone, | 27 | lbs. |
| The muscles, | 63 | lbs.,, |
| The viscera, with skin, fat, blood, etc., | 60 | lbs.,, |
The property of muscular tissue by which its peculiar functions are exercised, is its contractility—contraction or shortening. This is excited by all kinds of stimuli, applied either directly to the muscles, or indirectly to them through the medium of their nerves.
The muscular tissues perform all the physical work—as locomotion, every kind of action and exertion—of the body.
The quantity of blood circulated through the body is estimated to be from about 1⁄10 to about 1⁄13 part of the body’s weight, and about ¼ of that is distributed in the muscles.
As regards the action of the muscles the following general principles ought to be kept in view:
1. That the force exerted by any muscle during its contraction is in proportion to the number of muscular elements or fibers composing the muscle.
2. That the extent of motion, in so far as it merely depends on the shortening of the fibers of the muscle, is in proportion to the length of the fibers.
3. That the direction of the force produced by a contracting muscle is in the line of the axis of the whole muscle if it runs straight between its opposite points of attachment, but in the line of the portion attached to the moving part of the muscle, or its tendon, if it be bent in its course, etc.