530 MATER i A MEDIC A AND THERAPEUTICS. 



extremely complex, and indeed still very obscure. On this 

 account we have taken them last in the whole range of remedies, 

 and it will be found that they involve all the systems already 

 discussed, especially the nervous and circulatory. As a group 

 they are very heterogeneous, and we will select for special con- 

 sideration three distinct subjects, namely (1) Counter-irritants, 

 such as blisters ; (2) Baths ; and (3) Surgical Applications. 



I. PHYSIOLOGICAL RELATIONS. The physiological relations 

 of the surface of the body have already been studied under 

 several distinct heads. 



The nerves are connected not only with the sensorium, 

 but with the vital centres which regulate the vessels and 

 viscera. The cutaneous vessels have equally extensive relations. 

 They have the usual nutritive function ; they are the great 

 refrigerating apparatus of the body ; and they also serve as a 

 great external blood-reservoir, in connection with the systemic 

 circulation. 



II. PHARMACODYNAMICS. When the classes of measures 

 given at the ends of the chapters on the circulation and nervous 

 system are compared, it is found that several of them act on 

 both, and that their action may be different or even opposite 

 according to the time for which they are applied. For these 

 and other reasons, a number of them have been collected into a 

 special class, and called 



Counter-irritants. These measures may be thus 

 arranged, according to the degree of their action : 



1 . Eubefacients (rubere, to be red, and facere, to make) cause 

 increased redness and heat of the parts. Such are Hot Water ; 

 Mustard, and its preparations ; Ammonia, and its preparations ; 

 tiie confined vapour of Chloroform, Ether, and Alcohol ; all 

 Volatile Oils, especially Turpentine, Camphor, Menthol and 

 Thymol ; Iodine carefully applied ; Emplastrum Picis ; and 

 Emplastrum Calefaciens. 



2. Vesicants (vesica, a blister), Epispastics (eVt, upon, and 

 <rir(w, I draw), or Blisters, produce a rubefacient effect, fol- 

 lowed by the development of a blister. They include Cantha- 

 rides, Mezereon, Ammonia long applied or confined, Iodine, 

 Oil or Compound Liniment of Mustard, and Scalding Water. 



3. Pustulants (pus, matter) produce a crop of pimples. 

 They are a small group, consisting of Croton Oil, Tartar 

 Emetic, Nitrate of Silver in strong solution, and Ipecacuanha. 



