BACTERIA 81 



Finally a series of relief maps shows the growth and development of the 

 water supply of New York City, the location of the reservoirs and the 

 course of the new Catskill aqueduct- 

 Following the water-supply exhibit is a series of models illustrating 

 the dangers from improper disposal of the liquid wastes of the city 

 Disposal of and how they may be avoided. Actual points of danger 

 City Wastes in the neighborhood of New York are shown where 

 polluted harbor waters, bathing-places, and shellfish beds constitute a 

 menace to health. Modern methods for the treatment of sewage on 

 scientific lines are illustrated by a series of models of screens, sedimenta- 

 tion tanks, and filter beds of various types. 



The cases near the window are devoted to the group of Bacteria, espe- 

 cially in their relation to human life. Glass models show the various 

 „ . shapes and relative sizes of these minute forms, and in 



particular of the principal types which cause disease. In a 

 nearby case are displayed actual colonies of a number of species of 

 bacteria, including some which produce disease and others which are 

 beneficial to man by their effect upon soil fertility or from the fact that 

 they may be utilized in the production of substances useful as foods or in 

 the arts. A group of transparencies at this window shows some of the 

 more important disease bacteria as they appear under the microscope. 

 Another series of exhibits deals with the transmission of disease 

 by insects, notably by the fly and flea and by the mosquito. The 

 Insects most striking features are greatly enlarged models of the 



and Disease fly, the flea, the louse and the yellow fever mosquito. 

 Each of these, the finest models of the kind ever made, required a year 

 or more of constant, exacting labor. 



The egg, larva and pupa of the fly and the eggs of the louse are also 

 shown. 



Following the water-supply exhibit on the east side of the hall, the 

 relation of the flea and the rat to the terrible disease bubonic plague is 

 The Flea illustrated in considerable detail. Wall charts picture the 



and Bubonic spread of the great historic epidemics of this disease, and 

 Plague reproductions of sixteenth and seventieth century draw- 



ings show with what terror the Black Death was regarded in pre- 

 scient ific days. 



Specimens of some of the principal animals which harbor the plague 

 germ and serve as reservoirs from which it is carried by the flea to man 

 (the black, brown and roof rats, the wood rat and the California ground 

 squirrel) are shown, and the manner in which the disease is disseminated 

 is illustrated by a copy of a corner of a rat-infested house in California. 

 The original from which this was copied, as well as many of the rats 



