DRUGS WHICH ACT ON THE HEART. 469 



measures which, increase and diminish, respectively, the 

 work and nutritive activity of the heart. Rest in bed, avoid- 

 ance of walking, carriage exercise, movement on level ground, 

 are a descending series of means of giving the heart rest, and 

 the different kinds of wholesome muscular exercise are equally 

 valuable means of throwing work upon the heart, when its 

 condition demands increased activity. 



3. The Arteries. The peripheral resistance in the arteries 

 introduces us to a vast number of pharmacodynamical influences 

 which we must be content simply to enumerate : 



a. The vaso-motor centre can be stimulated directly by Alcohol 

 and Chloroform (temporarily), by Ether, Ammonia, Strychnia, 

 Digitalis, and Scilla ; by irritation of the sensory nerves in any 

 accessible part of the body for instance, by cold, counter-irri- 

 tants such as mustard, etc., applied to the calves or soles, by stimu- 

 lation of the trigeminus, the most ready and powerful means of 

 which is Ammonia held to the nose. On the other hand, the vaso- 

 motor centre may be directly depressed, by Alcohol and Chloro- 

 form in the second stage, by Opium, Chloral, Diluted Hydro- 

 cyanic Acid, Antimony, Ipecacuanha, Aconite, Belladonna and its 

 allies ; by muscular rest ; by emotional quiet and balance ; and by 

 local sedatives, such as anodynes, warmth, and gentle friction. 



b. The local vaso-constrictor mechanism in the arterial walls 

 is stimulated directly by Lead and Silver, Digitalis and Squill, 

 in the first stage, Ergot; and by local cold, produced by 

 irrigation with water, by Ether spray, or by evaporation of 

 spirituous, acid, and saline solutions, such as lotions of Rectified 

 Spirit, Vinegar, and Chloride of Ammonium. We call these 

 measures vascular astringents. 



Vascular dilatation may be effected through the same local 

 mechanism by the Nitrites of Amyl and Sodium, Nitroglycerine, 

 Alcohol, and Belladonna ; by the local heat afforded by poultices 

 and fomentations ; by the whole group of Volatile Oils, of which 

 Turpentine and Camphor are the types ; by Acrid Oils, including 

 Mustard and Mezereon ; by irritant metals and metalloids, such 

 as Zinc, Copper, and Iodine ; and artificial carbon compounds, 

 including Creasote, Carbolic Acid and their allies. Local vascular 

 dilators are naturally local circulatory stimulants. The con- 

 tinuous current also causes local vascular dilatation. 



4. The Capillaries. As one of the causes of peripheral re- 

 sistance, the condition of the capillary areas is an object of great 

 interest to the therapeutist. We can dilate the capillaries and 

 increase the flow through them by either local warmth or per- 

 sistent cold, by friction, and by local nervous irritants, such as 

 the confined vapour of Spirits, Mustard, Aromatic Oils, and other 

 rubefacients. This is but an early stage of the process of in- 



