604 OPEEATIONS ON THE FOOT. 



the caseous substance being also removed ; the same compressive 

 dressing to be put on again. 



The modification in the horny secretion, and the formation of 

 a layer of hardened and adherent horn, are especially great in the 

 parts where podophyllous and velvety tissues exist ; but are very 

 slow, and surrounded with difficulties in the median and lateral 

 lacunse of the frog. After ten days of treatment, one may have 

 brought about a normal secretion on the whole circumference of 

 the sole, on the inferior face of the os pedis, and on the prominent 

 parts of the pyramidal body. But in the lacunse the alteration 

 remains isolated, and resists treatment-; and it often happens that, 

 if neglected, it may again sj)read and the disease reach its former 

 extent. It is then the case, when the disease is limited to the 

 lacunse, to add to the ingredient already in use and which is kept 

 api^lied upon the restored parts, another stronger and more active 

 agent, sometimes simply absorbent; here again it becomes diffi- 

 cult for us to advise the practitioner, the number of recommended 

 drugs being very large and the result depending less on their 

 nature than in the intelligent and persisting manner with which it 

 is apphed. When caustics are used, it must be done with great 

 care, to Umit their action only to the thickness of the keratogen- 

 ous tissue, and not to carry it to the destruction of the bone, or 

 still worse, of the plantar aponeurosis. 



Let us glance at the drugs which have proved most successful 

 in the treatment of canker : First we have the different pyrogen- 

 ous preparations, especially wood tar, recommended by Bracy, 

 Clark, Eeynal and Bouley, and which give astonishing results. Gas 

 tar, oil of cade, petroleum and soot have also been used, but with 

 less advantage ; creosote and phenic acid have often shown them- 

 selves very useful, by penetrating easier to the base of the villosities 

 where the parasite resides and thus acting more regularly ; phenic 

 acid proved very useful with Krause, Gerlach and Zundel. 



After these the best recommended preparations are the salts of 

 iron. Hertwig seems to be well pleased with the powder of sul- 

 phate, and Ai-nold recommends the pyrohgnite of the same metal ; 

 Megnin advises sj^ecially the perchloride, which, like phenic acid, 

 is rather a powerful astringent than a true caustic. The jjrepar- 

 ations of copper have also had their time, and es^Decially the aceta- 

 tes, such as the cegyptiacum ointment (Girard, Schaack, Kainard 

 and Key) ; the baths of sulphate of copper were employed by 



