450 GENERAL ANATOMY. 



sleep, and in a state of paralyses; regard must also be had to 

 that which they take in general tonic spasm or in tetanus: 

 now, in having regard to these various considerations, it would 

 seem that the extensors are the preponderating muscles in 

 the trunk; in the jaw, the elevators; in the superior members 

 generally, the flexors; in the forearm, the pronators; in the 

 inferior members generally, the extensors; and in the feet, the 

 adductors. 



724. There are in the organization several circumstances* 

 unfavourable to the action of the muscles, and which diminish 

 their power of contraction or effective force to an efficacious 

 force, i. e. to a much less considerable result. These. circum- 

 stances, well ascertained since Borelli, are, 1st, the equal divi- 

 sion of muscular effort between its two attachments, whilst one 

 point alone in general is to be moved ; 2d, the unfavourable 

 lever, that of the third kind, by which a great part of the 

 power is lost; 3d, the oblique insertion of the muscles on the 

 bones, and of the fleshy fibres on the tendons ; 4th, the resist- 

 ance of the antagonist muscles ; 5th, the friction of the ten- 

 dons and that of the articulations. 



There are also in the organization, circumstances which, by 

 favouring muscular action, diminishes the influence of the 

 former: of this description are the change of the angle which 

 the muscles and the bone form, by means of certain anatomical 

 dispositions, as the volume of the articular extremities of the 

 bones, the existence of the apophyses at the place where the 

 muscles are attached, that of the sesamoid bones, &c. Such is 

 also the diminution of friction by the synovia, &c. 



Finally, the animal mechanism presents the same perfection 

 as that which is every where to be admired in nature. What 

 the muscle loses in force, motion gains in extent and rapidity, 

 by the employment of the lever of the third kind, and by the 

 obliquity of insertion. On the other hand, the obliquity of the 

 muscular fibres upon the tendons, by diminishing the extent 

 of motion, and even the force of the muscle, permits, under a 

 small volume, the union of a very great number of fibres, 



* J. Alph. Borelli, de motu animalium, opus posthumum. 



