3. The manner in which the division is produced by a wound, has nothing particular in it; that by a rupture, takes place in the following manner. A man leaps over a ditch, but his spring or exertion is too weak; he reaches the opposite bank only with the ends of his feet: the line of gravity not falling on the ground, the weight of the body throws the feet into a state of violent flexion, the muscles contract with great force, to prevent a fall backwards, and, at that instant, the tendon is ruptured, in consequence of being drawn downwards by the violent flexion of the foot, and upwards by the effort of the muscles: hence it appears that Petit was deceived with regard to the mechanical cause of the rupture, which he considered as taking place at the moment of the patient’s alighting on his feet, when, as he said, the tendons were surprised, so to speak, into a state of too great tension. It is easy to apply the principles of this particular case to others that may happen, and where the position may not be the same; such as, when we leap on a table, &c. Sometimes slighter efforts have produced the effect; and, as Louis observes, dancers have sometimes ruptured the tendo Achillis by making a powerful exertion on the point of the foot, as well as by other motions. 4. Divisions produced in the first mode, may be situated in any part of the tendon. Those produced in the second, occur more particularly about its middle: to that part the effort or strain is most forcibly determined, and there the resistance is the weakest. The rupture of the tendon may, according to Petit, be either complete or incomplete; but, if we consider the simultaneous contraction of the gastrocnemii and soleus muscles, and the intimate manner in which their two tendons are united at a considerable distance above the heel, it will be difficult to conceive how these tendons can be ruptured separately. With regard to divisions produced by cutting instruments, the case is different: there, the weapon may pass half way through the tendon either from behind or laterally; and perhaps divisions of this kind are much more frequently incomplete than otherwise, in consequence of the great resistance of the tendinous fibres. § II. OF THE SIGNS.