HACTF.lilA 87 



by 11 scries ol" »i;hiss inodcls. 'V\\v clTcct pioduccd hy llic j)()lluti()ii ol 

 water by iliscasc ^crins is illustrated by relief inai)s and dia<i;rams sliou- 

 injz; tlie course of famous tyi)lu)id and (Oiolera epideiiiics. .\b)(lels are 

 dis])layed wliicli illustrates the purification of water by storajz;e, filtra- 

 tion, and disinfection, the filter model beinj; an elaborate representation 

 of the plant at Little Falls, X. .1. l)ia<»;rams indicat(> the results of water 

 purification as measured in the savin<>; of human life. Finally a series 

 of five large relief maps show the growth and development of the water 

 supply of New York City. 



Following the water-sup])ly exhibit is a series of models illustrating 

 the dangers from improper disposal of the liquid wastes 

 r-^^^ w^ ° of the city and how they may be avoided. Actual points 



of danger in the neighborhood of New York are sho\vn 

 where polluted harbor waters, bathing-places, and shellfish beds consti- 

 tute a menace to health. Modern methods for the treatment of sew- 

 age on scientific lines are illustrated by a series of models of screens, 

 sedimentation 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 hfe. Glass models show 



Bactena . 



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 utiUzed in the production of substances useful as foods or in the arts. 

 A group of transparencies at the window shows some of the more im- 

 portant 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 



most striking features are greatly enlarged models of the 



^^^ ^ fly, the flea, and the louse. These, the finest models of 



Disease ^^^ ^m^ ever made, w^ere prepared by the late Ignaz 



Matausch from his original studies, and required several 



years of constant, exacting labor. 



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

 also shoT\Ti. 



Models in the wall case deal with the life history of the fly, showdng 

 its various stages in their natural size and actual habitat, and illustrate 

 the large numbers of flies which may breed in a single pound of manure 

 and the enormous progeny which may spring from a single pair and their 

 descendants during the breeding season. 



The deadly work of the fly in carrying typhoid fever is illustrated by 



