CHAPTER XX 

 CAUSTICS 



Synonym. Escharotics 



These are agents which act by causing the death of tissues. The 

 action of caustics produces a stronger degree of irritation than pus- 

 tulation. This action may be due to inflammatory necrosis or to 

 direct chemic action consuming the tissues (sulphuric acid), or pre- 

 cipitating the proteids (phenol). Tissue destroyed by chemical 

 agents will always be preceded by inflammatory necrosis and chemic 

 cauterization will always show three areas: the first or outside area 

 of hyperemia and inflammation, inside this a layer or zone of 

 necrotic tissue, and in the center a solution of cells which have been 

 killed by inflammatory processes. These areas should be regarded 

 in the light of different successive stages of the same action, and by 

 proper dilution, the first or second stages may be produced without 

 the succeeding ones. 



Some of the caustics, such as arsenic, mercury, the stronger alka- 

 lies, acids and bromine, act by forming soluble compounds with the 

 proteids of the tissues, while others, as most of the metallic salts, 

 saline and organic irritants, kill the cells by precipitation of their 

 proteids. If the corrosion leads to a loss of tissue, an infiammatory 

 exudate will be thrown upon the surface, where it will coagulate. 

 This exudate plus the products of the action of the irritant upon it 

 and upon the cells, form the scab or eschar. This will vary in form 

 with the nature of the chemical products forming it. Thus if the 

 irritant exerts a solvent action on proteids, as in the case of the 

 alkalies, the scab will be liquid, while if the product formed by the 

 agent upon the proteids is insoluble, as in the ease of metallic salts, 

 the scab will be hard. This fact is very important because it deter- 

 mines the depth of the action of the irritant. If the scab is soft the 

 irritant will penetrate it. Consequently the action cannot be con- 

 trolled and will spread and extend deeply. On the other hand, if the 

 scab is insoluble or hard it prevents deep penetration and the action 

 can be easily controlled or confined to the desired areas. This ex- 

 plains why the strong alkalies are not practical for purposes of irri- 

 tation, caustic action, etc., and why the metallic salts are to be pre- 

 ferred for these actions. 



Caxistics produce the same action upon the mucosfe of the intes- 

 tinal tract if swallowed as upon the skin. The early symptoms begin 



