324 



lique direction, the aponeurotic expansion formed by the tendinous cord, 

 as it penetrates into the muscular mass; now their action being exerted 

 in a direction more or less oblique, is decomposed and none is advanta- 

 geously employed, but that which takes place in the direction of the ten- 

 don. The muscles frequently pass over several articulations, in their 

 way to the bone which they are to move ; a part of their power is lost, in 

 the different degrees of motion on each other, of the parts on which 

 the bone rests into which the muscles are inserted. All these organic 

 imperfections are attended with an enormous misapplication of power 

 and with a waste of the greater part of it. It has been reckoned, that 

 the deltoid muscle employs a power equal to 2568 pounds to overcome a 

 insistence of 50. We are not to imagine, however, that there is a Ijss 

 of 2518 pounds ; for the deltoid muscle acting both on the shoulder and 

 on the arm, about one half of its power is employed on each of these 

 parts ; hence it is said, that in estimating the whole power of a muscle, 

 one should double the effect produced by its contraction, its action being 

 applied, at the same time, both on the weight which it raises, or on the 

 resistance which it overcomes, and on the fixed point to which its other 

 extremity is inserted. 



If the muscles were quite parallel to the bones, they would be incapable 

 of moving them, in any direction. On this account Nature has, as much 

 as possible corrected the parallelism, by removing, as we shall see, in 

 speaking of the osseous system, the tendons from the middle line of di- 

 rection of the bones, and by augmenting the angles at which they are in- 

 serted into them, either by placing, along the course, bones which alter 

 their direction, as the patella and the sesamoid bones; by increasing the 

 size of the articular extremities of the bones, or by pullies, over which 

 the tendons or the muscles themselves are reflected, more or less com- 

 pletely, as is the case with the circumflexus palati and the obturator in- 

 ternus. 



Nature has not, therefore, neglected mechanical advantages as much 

 as one might be led to imagine, on a slight examination of the organs of 

 motion. And if it be considered, that in the different conditions of life, 

 we do not require strength so much as rapidity of motion, that the power 

 might be gained by increasing the number of fibres, while it was impos- 

 sible to obtain velocity, by any other means than by employing a parti- 

 cular kind of lever, and that, in short, to give our limbs the most advan- 

 tageous form, it was necessary that the muscles should be applied to the 

 bones, it will be confessed, that in the arrangement of these organs, Na- 

 ture, in frequently sacrificing power to quickness of motion, has conci- 

 liated, as much as possible, these two almost irreconcileable elements. 



Though the lever of the third kind is that most frequently employed in 

 the animal economy, the two other kinds of lever are not altogether ex- 

 cluded from it ; there are even limbs which represent different levers, ac- 

 cording to the muscles which set them in motion ; thus, if we take the 

 foot as an instance, it will present us with levers of every kind. The 

 foot, when raised from the ground and held up and raised towards the 

 leg, form,s a lever of the first kind; the fulcrum is in the articulation and 

 separates the power, which is at the heel, from the resistance which is 

 at the tip of the foot that points downwards ; if this end of the foot rest 

 on the ground, and if we stand on tip-toe, they are changed into levers of 

 the second kind ; the power continues at the heel, but the fulcrum is re- 

 moved to the other extremity of the lever, and the resistance to the mid- 

 dle; and this resistance is very considerable, since the whole weight of 



