THE LUNGS AND AIR PASSAGES. 481 



4. The Lungs and Air-passages. (a) The afferent or sensory 

 nerves of the respiratory organs are stimulated by cold and dry 

 air, Chlorine gas, Ipecacuanha, Senega, Tohacco, Nitre fumes, 

 Ammonia, and Antimony. They are depressed or soothed by 

 warm and moist air, warm food, -warm applications to the chest 

 wall; possibly by demulcent substances to a small extent; and by 

 Opium, Chloral, Chloroform, and Ether. Sensations connected 

 with the respiratory organs may be modified by the same 

 means, the nerve-depressants thus proving to be pulmonary 

 anaesthetics or anodynes, as well as interfering with reflex 

 respiratory acts. 



(b) The vessels of the bronchi may have the circulation 

 through them increased by all measures which increase the 

 activity of the circulation generally, viz. by purgation, exercise 

 of the lungs, and bodily movement ; by Digitalis, Scilla, Am- 

 monia, Alcohol, Strychnia, and probably the whole series of 

 Aromatic Oils to be presently noticed. Per contra, the bronchial 

 circulation may be depressed by all cardiac and general vascular 

 depressants, including heat, Alkalies, Iodides, Aconite, Anti- 

 mony, and Ipecacuanha. 



(b'} The pulmonary circulation bears very complex relations 

 to the respiratory movements, as regards the pressure and rate 

 of flow in inspiration and expiration, ordinary and extra- 

 ordinary. Manifestly as regards the general circulation, the 

 pulmonary vessels may be modified by every influence which 

 affects it, such as blood-letting, transfusion, purgation, a variety 

 of drugs, and muscular rest or exercise. "We possess one 

 substance, non-officinal, which specifically contracts the pul- 

 monary vessels, namely Muscarin, the active principle of the 

 mushroom. 



(c) Glands of the bronchi. The secretion of bronchial mucus 

 may be increased by alkalies, especially Ammonia ; by Iodine, 

 Sulphur, and Antimony ; by Ipecacuanha, Senega, Tobacco, Scilla, 

 and the great group of Aromatic Volatile oils, Oleo-resins, and 

 Balsams, including Turpentine, Camphor, Benzoin, Copaiba, 

 Ammoniacum, and the balsams of Peru and Tolu. Warm 

 liquid food remarkably increases the bronchial secretion ; on 

 the contrary, cold dry food diminishes the bronchial mucus, 

 as possibly do Belladonna, Stramonium, and Hyoscyamus, and 

 certainly acids. 



(d) The nervo-muscular structures of the bronchi and larynx 

 are stimulated by those measures which act upon the afferent 

 nerves (a) and perhaps they are also directly influenced by 

 some of the same. 



A group of substances of great therapeutical interest directly 

 depress the same system, and so relax the bronchial walls and 

 2 F 8 



