338 



DISEASES OP THE FEET. 



bones, brought about by the application of Bhoes "which are 

 either turned down, calkined, or made thicker at the heels 

 than at the toes. 



'2/ ■ . c 



Fio. 60 represents the bones when their position is altered by^ 

 thick -heeled shoe ; the line is changed from its natural oLliquity to a^ 

 direction approaching the perpendicular. The iDwer eni of the os 

 coron® (b) ia made to rest upon the navicular (d), as well as uprn the 

 pedal bone (e). The navicular bone is made to bear weight for which 

 it was not intended, neither \f> its structure calculated tv do so. All 

 Weight -bearing bonen ha^e their fibres arranged to receive weight 

 Upon thoir extremities, but the fibren ^{ the navicular, and cf all the 

 Besamnicican bones or muscular appendages, are njt bo arranged, and 

 weight thrown upon them Induoos dlaeaae. 



The^ development of navicular lameness from rheumatoid 

 disease ia occasionally due to what Professor Dick termed 

 " occasional exercise," which implie3 lon;» periods of rest, inac- 

 tivity, and irregular work. Professor Dick maintained that 

 during rest there was a deficiency of synovial secretion, and 

 that when an animal, with his joints and bursa? in this dry 

 condition, was suddonly put to fast work, the effects of tha 

 friction upnn the surface of tendon, moving under the bone, 

 were laceration of ita libres and navicular disease. Whether 



