IN THE HUMAN FRAME. 67 



strength ; so it cannot be cut, except by an accident which 

 wouhi sever the limb. If I had been permitted to frame a 

 proof of contrivance, such as might satisfy the most dis- 

 trustful inquirer, I know not whether I could have chosen 

 an example of mechanism more unequivocal, or more free 

 from objection, than this ligament. Nothing can be more 

 mechanical ; nothing, however subservient to the safety, 

 less capable of being generated by the action of the joint. 

 I would particularly solicit the reader's attention to this 

 provision, as it is found in the head of the thigh bone ; to 

 its strength, its structure, and its use. It is an instance 

 upon which I lay my hand. One single fact, weighed by 

 a mind in earnest, leaves oftentimes the deepest impres- 

 sion. For the purpose of addressing different understand- 

 ings and different apprehensions, for the purpose of senti- 

 ment, for the purpose of exciting admiration of the Crea- 

 tor's works, we diversify our views, we multiply examples ; 

 but, for the purpose of strict argument, one clear instance 

 is sufficient : and not only sufficient, but capable, perhaps, 

 of generating a firmer assurance than what can arise from 

 a divided attention. 



The ginglymuSj or hinge joint, does not, it is manifest, 

 admit of a ligament of the same kind with that of the ball 

 and socket joint, but it is always fortified by the species of 

 ligament of which it does admit. The strong, firm, invest- 

 ing membrane above described, accompanies it in every 

 part j and, in particular joints, this membrane, which is 

 properly a ligament, is considerably stronger on the sides 

 than either before or behind, in order that the convexities 

 may play true in their concavities, and not be subject to 

 slip sideways, which is the chief danger ; for the muscular 

 tendons generally restrain the parts from going further 

 than they ought to go in the plane of their motion. In the 

 knee^ which is a joint of this form and of great importance, 

 there are superadded to the common provisions for the 

 stability of the joint, two strong ligaments which cross 

 each other, and cross each other in such a manner, as to 

 secure the joint from being displaced in any assignable di- 

 rection. [Plate XI. fig. 2, 3, 4.] " I think," says Che- 

 selden, *' that the knee cannot be completely dislocated 

 without breaking the cross ligaments."* We can hardly 

 help comparing this with the binding up of a fracturd, 



* Ches. Anat. ed. 7th, p. 45. 



