FORMATION OF MUCUS IN THE RESPIRATORY PASSAGES. 273 



0'54^07 per 1000; in badly ventilated sick chambers = 2'4; in overcrowded 

 auditoriums, 3 '2 ; in pits = 4'9 ; in school-rooms, 7 '2 per 1000. Although it is not the 

 quantity of C0 2 which makes the air of an overcrowded room injurious, but the 

 excretions from the outer and inner surfaces of the body, which give a distinct 

 odour to the air, quite recognisable by the sense of smell, still, the amount of C0 2 

 is taken as an index of the presence and amount of these other deleterious sub- 

 stances. The question as to whether the ventilation of a room or ward occupied 

 by persons is sufficient, is ascertained by estimating the amount of C0 2 . A room 

 which does not give a disagreeable, somewhat stuffy, odour has less than 0'7 per 

 1000 of C0 2 , while the ventilation is certainly insufficient if the C0 2 = 1 per 1000. 



As the air contains only 0'0005 cubic meter C0 2 in 1 cubic meter of air, and as 

 an adult produces hourly '0226 cubic meters C0 2 , calculation shows that every 

 person requires 113 cubic meters of fresh air per hour, if the C0 2 is not to exceed 

 0'7 per 1000 : for 0'7 : 1000 = (0'0226 + x x O'OOOS) :x, i.e., x = 113. 



In ordinary rooms, where every person is allowed the necessary space (1000 cubic 

 feet) the air is sufficiently renewed by means of the pores in the walls of the room, 

 by the opening and shutting of doors, and by the fireplace, provided the damper 

 is kept open. 



It is most important to notice that the natural ventilation be not interfered with 

 by dampness of the walls, for this influences the pores very greatly. At the same 

 time, damp walls are injurious to health by conducting away heat, and in them the 

 germs of infectious diseases may develop (Lindwurra). 



138. Formation of Mucus in the Respiratory 

 Passages Sputum. 



The respiratory mucous membrane is covered normally with a thin 

 layer of mucus (Fig. 97). By its presence this substance so far inhibits 

 the formation of new mucus by protecting the mucous glands from the 

 action of cold or other irritative agents. New mucus is secreted as that 

 already formed is removed. An increased secretion accompanies con- 

 gestion of the respiratory mucous membrane. Division of the nerves 

 on one side of the trachea (cat) causes redness of the tracheal mucous 

 membrane and increased secretion (Rossbach). 



Effects of reagents on the mucous secretion. If ice be placed on the belly 



of an animal so as to cause the animal to " take a cold" the respiratory mucous 

 membrane first becomes pale, and afterwards there is a copious mucous secretion, 

 the membrane becoming deeply congested. The injection of sodium carbonate 

 and ammonium chloride limits the secretion. The local application of alum, 

 silver nitrate, or tannic acid makes the mucous membrane dry, and the epithelium 

 is shed. The secretion is excited by apomorphin, emetin, pilocarpin, and 

 ipecacuanha, while it is limited by atropin and morphia (Rossbach). 



Normal Sputum. Under normal circumstances some mucus mixed 

 with a little saliva may be coughed up from the back of the throat. 

 In catarrhal conditions of the respiratory mucous membrane, the sputum 

 is greatly increased in amount, and is often mixed with other character- 

 istic products. Microscopically, sputum contains : 



1. Epithelial cells chiefly squames from the mouth and pharynx 



18 



