408 HEALTH AND DISEASE 



their secretion lessened by alkalis. From these considerations the reason 

 for giving alkaline tonics before meals, and acids after them, will be obvious 

 to the reader. 



In the section on the physiology of digestion it has been explained 

 how the fluids of the first portion of the duodenum act upon the partially 

 digested food as it leaves the stomach, and here again the remedies under 

 consideration continue their work. The continued employment of acids 

 for a length of time is not desirable, as they may establish an artificial 

 need for them, or result in catarrh of the stomach. 



Besides the use of acids in various forms of indigestion, they are 

 serviceable for their constringing action upon the lining membrane in 

 cases of diarrhoea with a tendency to pass blood. Dilute sulphuric acid 

 is generally preferred, or an old-fashioned aromatic acid in which ginger 

 and cinnamon play a not unimportant part. 



Sulphuric acid is given to arrest liEemorrhage in different organs, as 

 the liver, kidneys, uterus, and lungs. 



For all the purposes previously named it will be understood that the 

 dilute acids of the Pharmacopoeia are implied, the strong preparations 

 being destructive caustics, and on account of this property being sometimes 

 employed to remove warts and check the progress of malignant growths. 

 If used as escharotics, care should be exercised in not allowing them to 

 come in contact with healthy parts, or to burn the hand of the person 

 making use of them. 



DRUGS WHICH ACT ON THE LUNGS AND AIR- 

 PASSAGES 



The respiratory apparatus may be influenced in two principal directions 

 by the administration of drugs, which may be divided into stimulants and 

 depressants. The reader who would properly understand their modus 

 opera7idi is referred to the chapter dealing with the physiology of the 

 breathing organs. 



It will be there seen that the minute blood-vessels of the luno-s are 

 spread over the walls of the air-vessels which constitute the parenchyma 

 or lung substance in the form of a net-work, where it is brought into 

 contact with the air inspired, or with gases accidentally or intentionally 

 drawn into the lungs in the act of inspiration. 



The diameter of the minute air-tubes is capable of being increased or 

 diminished by their involuntary muscular fibres, while the larger tubes 

 derive greater firmness from the presence of rings of cartilage which pre- 

 vent them from being altogether closed under any circumstances. 



