208 



MR. J, U. SUTTON ON DISEASES OF 



[Apr. 20, 



suffer at some period of their life from those troublesome thickenings 

 of the skin of the feet and toes known as corns. Structurally a 

 corn consists of thickenin» of the epidermis, due to pressure of an 

 intermittent character, often the result of badly fitting boots. In 

 many cases a small sac containing fluid may be detected between 

 the thickened epidermis and the deeper tissues ; this sac is techni- 

 cally termed a bursa. In others the bursa is replaced by loose 

 connective tissue which allows the corn to glide freely over the 

 underlying structures. We find excellent examples of corns in the 

 ischial callosities of the Cynomorj}ha and in the callous pads found 

 on the feet of Carnivora. 



Fi- 1. 



The right funiculai- pouch of peritoneum of Macacus sinicus, occupied by a 

 plug of omentum, o ; the testis, t. 



Of late years the attention of surgeons has been directed to corns, 

 in consequence of a very remarkable affection to which they are 

 liable. Under certain abnormal conditions of the spinal cord and 

 peripheral nerves, such as locomotor ataxy, sclerosis, and peripheral 

 neuritis, the corns ulcerate, and at last the ulceration perforates not 

 merely the corn, but the whole thickness of the foot; hence it is now 

 iamiliar as the " perforating ulcer." 



It was to me a matter of no small interest to find the callous pad 

 on the foot of a Civet Cat the seat of a perforating ulcer ; the 

 interest was considerably heightened when, on opening the spinal 



