ON THE NAVICULAR DISEASE AND NEUROTOMY. 
80 
is frequently so extensive, that after the nerves have been divided, 
the friction which takes place divides the tendon, and the pas¬ 
tern falls to the ground. Mr. Turner states that he has seen 
cases where the tendon has given way immediately on the animal 
being allowed to get up; and therefore considers that in such 
cases friction could not have been the cause. He also observes, 
that he has seen cases where the tendon has been so attenuated 
by absorption, that he could see distinctly through the few re¬ 
maining fibres. 
Never having met with a case where the tendon has given way 
so immediately after the operation as in those mentioned by 
Mr. T., I have not alluded to them, but those he has mentioned 
do not induce me to alter my opinion. 
If a fresh rope was made to pass over a pulley (which the navi¬ 
cular bone may represent), and was attached to a resisting body, 
and if the pulley in course of use, instead of having the smoothest 
possible surface, was to become worm-eaten, and to put on a 
ragged surface, the friction would be such as soon to destroy the 
rope; but if (the machine was so admirably constructed, that the 
engineer, although he could not restore the sound state of the 
parts, could, by throwing a little more of the weight upon the 
other ropes and tackle, still keep the machine in motion, and at 
the same time save the injured part; and if, after a time, the 
engineer could, by some means or other, be led to suppose that 
the pulley and rope had been made as sound as ever (while, on 
the contrary, the rope had continued to waste, and the pulley to 
have become rougher than at first); and if, under such circum¬ 
stances, the strain was to be thrown at once upon these parts, what 
might we expect to be the consequences ?—why, that, by the first 
movement, the rope would be sawn through. 
That friction is the cause of the attenuation and absorption of 
the tendon at the part alluded to, I am induced to believe, from 
the appearance which it presents in such cases, as mentioned by 
Mr. T urner, for I have found portions of the tendons on the sur¬ 
face next the navicular bone exhibiting the appearance of several 
of the fibres of the tendon having been divided, as it were, 
about the centre of the bursa, retiring upwards and downwards, 
and coiled up, or the ends of the fibres rounded, as if from the 
play of the parts ; in other cases the appearance of a separation 
of fibres longitudinally, similar to what is shown when a tendon 
taken from the dead subject has been drawn several times over 
a rough surface. Such appearance I have no doubt Mr. T. 
must have observed in his minute examination of these cases. 
It must here be observed, that the operation of neurotomy re¬ 
duces the foot to the state of an inanimate machine, and I am 
