44 
The proportion of cases among persons at residences of which all 
the sanitary conditions were good has progressively diminished 
during the last tliree years. 
In all three years the majority of the cases occurred among persons 
living at residences of good or fairly good sanitary conditions, but 
this majority has diminished from year to year. Thus, the percent- 
ages of cases at residences where the sanitary conditions were good 
or fairly good were: 1906, 66.3 per cent; 1907, 62.2 per cent; 1908, 
53.1 per cent. 
These figures suggest that since 1906 there has been here a diminu- 
tion in the part played by agents such as disseminate the infection 
of ty]3hoid fever generally in a community, and that the part played 
by agents such as affect especially persons living under the poorer 
sanitary conditions has been relatively increased. 
In this connection it is interesting to note that the sanitary con- 
dition of the residences of the 52 cases this season definitely attrib- 
uted to milk-borne infection was as follows: Good, 24; fairly good, 
23; rather bad, 5; bad, 0. 
DISPOSAL OF SEWAGE. 
Of the 542 cases this season, 483 were among persons living at 
residences connected vdth the city sewerage system and at which 
there were water-closets, 56 at residences not connected ^vith the city 
sewerage system and at which there were privies, 1 at an institution 
not connected vdth the city sewerage system but having water-closets 
which discharged into a local sewerage system, and 2 on a dredge the 
water-closets of which discharged into the Potomac River. 
The follo^ving table shows the methods of disposal of sewage at the 
residences of the cases studied during the three years : 
Sewage disposal. 
Number of cases. 
1908. 
1907. 
1906. 
Residence connected with city sewerage system and having water-closets 
483 
462 
671 
Residence not connected vnth city sewerage system and at which there were 
privies 
56 
56 
72 
Residence having neither water-closets nor privies 
0 
1 
2 
Residence having water-closets which discharge into subsoil cesspool 
0 
1 
1 
Residence having water-closets which discharge into local sewerage svstem 
3 
3 
0 
Method not noted 
0 
0 
1 
Total 
I 542 
523 
747 
