384 PRACTICAL ANATOMY. 



materials which are flexible. Their strength has to be equal to the 

 accidental force applied, tending to dislocate the parts which they unite. 

 Most of our muscles, with their tendons, become, indeed, principally 

 the ligaments in the motions of the joint, arising from their own action. 

 But every joint is not sufficiently surrounded with muscles and tendons 

 to guard it in eveiy direction; therefore it must have ligaments as a substi- 

 tute. The thigh-bone at the union with the pelvis, and the humerus at the 

 union with the scapula, are so surrounded with muscles that it is hardly 

 necessary for them to have ligaments, excepting to retain the synovia. 

 However, as those large joints are subject to various motions, not pro- 

 duced by their muscles, it was necessary they should have ligaments of 

 some strength ; although these are not always equal to the force of such 

 motions, which are commonly called accidental. The ligaments of joints 

 are inserted at a distance from the moving point, in a proportion equal 

 to the quantity of motion, which motion is always from the received 

 bone, viz. the thigh-bone and the humerus. It is equally so in the 

 ginglymus and conoid joints ; for, in the ginglymus, the ligament is 

 inserted at a great distance from the point of motion on the flexing and 

 extending sides, but is much nearer to the lateral, and in the true 

 conoid the ligaments are inserted at equal distances all round. 



The vertebras of the quadruped are never, in any action of the animal, 

 in danger of being pulled asunder, but they are liable to be broken 

 asunder ; therefore the union of the two is such as is a hindrance to 

 their being broken, the strong part of the union being exterior, and the 

 weak one in the centre. 



The simple motion in every joint is the sliding one; but from the 

 difference in the articulations, and the different directions of the bones, 

 different effects are produced, which have given rise to different classes 

 of joints, and of course to different names for them 1 . 



[Practical Anatomy.] 



Of the Arrangement of Anatomical Preparations. 



Parts of animals are often so combined, in their connexions and uses, 

 as to make it impossible to separate them so as to make a series of 

 anatomical preparations, perfectly classed according to their uses only ; 

 the vesica urinaria, e. g., is connected entirely with the kidneys, as to 

 use ; but is so connected with the penis, &c. as to situation, as to make 

 them inseparable. The urethra belongs equally to both. 



1 [The work had not proceeded beyond the second chapter. The following is a 

 supplemental one on practical anatomy, or the art of making and arranging 

 anatomical preparations.] 



