TONICS 137 



specially serviceable in anaemia ; phosphates are prescribed 

 for ill-thriving, weakly young animals ; salines are indicated 

 in skin eruptions and itching, often met with amongst hard- 

 worked, liberally-fed horses ; pepsin, peptonised milk, liquor 

 pancreatis, and malt extract, are sometimes administered to 

 foals, dogs, and calves, when the natural digestive ferments 

 are deficient or faulty. 



TONICS. When digestion is enfeebled, nutrition impaired, 

 circulation languid, or waste products not promptly removed, 

 there is apt to ensue weakness, want of energy, and unfitness 

 for work conditions treated for the most part by tonics. 

 They are defined as remedies which impart tone or strength 

 to the parts on which they specially act. They are allied to 

 nutrients and restoratives. They resemble stimulants ; but 

 their effects are more slowly and gradually produced, are 

 more permanent, and not succeeded by subsequent depres- 

 sion. While stimulants usually call forth strength previously 

 latent, tonics frequently give strength. The same drugs, 

 in different doses, often appear, however, in two or more of 

 these classes. Alcohol, for example, is nutrient, tonic, and 

 stimulant. Iron salts, according to their dose and the state 

 of the patient, are nutrient, tonic, and astringent, but, used 

 improperly, are sometimes irritant. 



Tonics exert their curative effects in one or more of the 

 following ways : 



1. By influencing digestion directly, usually increasing 

 gastric secretion. Gentian, calumba, chiretta, and other 

 bitters are chiefly serviceable as gastric stimulants or 

 stomachics. 



2. By indirectly assisting digestion, by improving the 

 chemical and physiological condition of the blood, secretions, 

 and tissues. The most important members of this class are 

 hsematinics, noticed below. 



3. By acting on other special organs and structures, 

 notably on the heart, nervous centres, or liver. 



In using tonics it is accordingly essential to discover what 

 part or organ is primarily and chiefly at fault. When diges- 

 tion is enfeebled, gastric or intestinal tonics are prescribed. 

 When the pulse is soft and weak, with a tendency to local 

 congestion and oedema, cardiac and vascular tonics are used. 



