168 DISEASES OF THE HOHSE'S FOOT 



repeated expansion of the wall posterior to the crack, with 

 the portions anterior to it in a state of enforced quiescence, 

 leads in time to the posterior edge of the crack coming to 

 lie over that of the anterior. 



Complications. — The first complication likely to arise in 

 a case of sand-crack is that attending simple laceration 

 of the sensitive structures in a deep lesion. With the 

 laceration all the phenomena of a repairing inflammation 

 make their appearance. As a result, there is more or less 

 heat according to the degree of inflammatory hypersemia, 

 swelling according to the amount of inflammatory exudate, 

 and pain according to the amount of pressure the two fore- 

 going bring to bear on the nerves in the inflamed area. 



A second and more serious complication is the greater 

 inflammation set up by the introduction into the crack 

 of foreign substances. Small portions of gravel and flint, 

 both by the irritation set up by their friction and by the 

 infection they carry in with the dirt surrounding them, are 

 responsible for the mischief. 



When, from direct communication with the blood-stream, 

 due to extensive haemorrhage, bacteria from the outside gain 

 entrance, this simple inflammation is further complicated 

 by the formation of pus, or a limited gangrene of the 

 keratogenous membrane. 



In cases of great severity the gangrene of the kerato- 

 genous membrane spreads until the deeper structures are 

 involved. We then get a necrosis (in the case of toe-crack) 

 of the extensor pedis, and sometimes caries of the os pedis. 



In like manner the necrotic changes occurring under 

 these circumstances may invade the deeper structures in 

 the region of quarter-crack. As a result of this, we may 

 have the starting-point of suppurating corn, or necrosis of 

 the lateral cartilage — in other words, cartilaginous quittor. 



Commonly accompanying quarter-crack is the condition 

 of contracted heels and atrophied frog. Sometimes de- 

 scribed as a complication of sand-crack, it appears to us 

 more rational to rather regard the sand-crack as a result 

 or complication of the vice of contraction. 



