114 ON SOME OF THE CAUSTICS 



1st. Those which act by the complete destruc- 

 tion of the tissues with which they come in 

 contact. 



2nd. Those which act by entering into chemical 

 combinations with the components of the tissues. 



In the first class are comprised the mineral 

 acids, which exert a powerful affinity for the 

 water which constitutes four-fifths of the weight 

 of the animal tissues ; the caustic alkalies, which 

 dissolve albumen, fibrin, and gelatine; and the 

 actual cautery. 



Under the second head are included the metallic 

 compounds which act as caustics; such as sulphate 

 of copper, bichloride of mercury, nitrate of silver, 

 chloride of zinc, chloride of antimony, arsenious 

 acid, &c. 



In the practice of dental surgery, caustics are 

 employed in two classes of cases : — 



I. — In the treatment of various unhealthy 

 conditions of the mucous membrane of the mouth. 

 These conditions, however, so generally arise from 

 constitutional causes, that they come more into 

 the province of the surgeon, and I propose, there- 

 fore, to confine myself to, — 



II. — The treatment of diseased conditions of the 

 dental tissues themselves. We may subdivide 

 this class into, — 



1st. Those cases where it is only required to 

 lessen the sensitiveness of the dentine or cemen- 

 tum ; and, — 



