246 RENEWAL OF THE AIR IN LIVING-ROOMS. 



the work must be done in a dusty atmosphere, and they are thus rendered detri- 

 mental to health. Charcoal-burners, grinders, stone-cutters, file-cutters, weavers, 

 spinners, tobacco-workers, sawyers, millers, bakers, and others suffer from various 

 affections of the lungs, induced by the dust of their trades. During a year's work 

 a workman in a horse-hair mill inhales 15 grams of dust, in a saw-mill 27 grams, 

 in a woolen mill 30 grams, in a grinding mill 37.5 grams, in an iron-foundry 42 

 grams, in a snuff-factory 108 grams, in a cement-factory 336 grams. 



The ciliated epithelium is exceedingly sensitive to mechanical excitation. The 

 coordinated, continuous movement of the cilia on a larger surface does not depend 

 wholly upon an external (mechanical) conduction of the stimulus, but also upon 

 an internal conduction (as in the nervous system). 



There is no doubt that with the inspired air the germs of infectious diseases 

 are often taken into the respiratory organs, whence they gain entrance into the 

 body. Thus, the diphtheria-bacillus becomes localized in the pharynx and the 

 larynx, the glanders-bacillus in the nose, the germ of whooping-cough in the bronchi, 

 the microbes of hay-fever and ozena in the nose, the influenza-bacillus in the air- 



Outer layer 



Intermediary forms 



Inner layer 

 Squamous cells 



FIG. 91. Stratified Ciliated Cylindrical Epithelium of the Larynx (Horse) (after Toldt). 



passages, the pneumonia-bacilhis in the air- vesicles. The cause of tuberculosis, 

 the bacillus tuberculosis, enters the air-filled pulmonary tissue with the dust of 

 tuberculous sputa, and may spread from that focus through all of the tissues. In 

 a similar manner leprosy arises from the bacillus lepras. The cause of malaria, 

 the plasmodium malariae possessed of ameboid movement, reaches the blood 

 partly through the respiratory organs, changes the hemoglobin within the red 

 corpuscles into melanin, and causes their destruction. In the same way the 

 blood is invaded by the exciting agents of smallpox (micrococcus vaccinas), 

 the spirillum of relapsing fever, the still little known microbe of measles, and the 

 as yet undiscovered germ of scarlet fever, etc. 



Many disease-germs enter the mouth with the air, others with the food, and 

 are swallowed, so that they undergo development in the intestinal tract. This is 

 true of cholera (comma-bacillus), dysentery, typhoid fever (bacillus typhosus), 

 and amebic enteritis (amceba coli; the amceba coli mitis is less virulent, and the 

 amceba intestina vulgaris is harmless). In cattle, anthrax arises in the same way 

 from bacterium anthracis. 



RENEWAL OF THE AIR IN LIVING-ROOMS (VENTILATION). 

 EXAMINATION OF THE AIR. 



Fresh air is one of the most necessary conditions for salutary existence on the 

 part both of the healthy and of the sick. It may be assumed that a sufficient 

 renewal of the air in living-rooms will be assured, if 800 cu. ft. of space be allowed 

 for every inmate of a room, and about 1000 cu. ft. for every sick person. The neces- 

 sary space for the inmates of dwellings, schools, barracks, penal institutions, and 

 hospital-wards should be measured accordingly, and the allotment of space to the 

 individuals should be made only in this proportion. However, this standard has 

 been materially departed from in various countries. 



In overcrowded spaces the amount of carbon dioxid at first increases. The 

 normal amount in the air (0.5 in 1000) has been found increased in comfortable 

 living-rooms to from 0.54 to 0.7 in 1000; in badly ventilated sick-rooms to 2.4 

 in 1000; in overcrowded auditoriums to 3.2 in 1000; in pits to 4.9 in 1000; in 

 school-rooms to 7.2 in 1000. Although it is not the amount of carbon dioxid 



