142 
Use of Town Sevmqe as Manure. 
when calculated on the dried mass, give the numbers 5"59, 4 34, 
and 7'13 ; but it must be remembered that these results refer to 
men in a middle station of life, whose excrements would pro- 
bably be richer in nitrogen than those of a poorer popula- 
tion. It is well known that, in addition to the food required for 
the sustenance (strictly so called) of the animal body, a large 
portion is required for the purposes of respiration. A given 
amount of bulk in the food is also by habit, as well as function- 
ally, a necessity of the stomach. With the poor, whose food is 
principally vegetable, and whose necessities compel the use of a 
minimum of nitrogenous food, the waste of nitrogen in the faeces 
must be comparatively small. The elements of respiration and 
the bulk of food necessary to fill the stomach are both in this 
case derived from carbonaceous materials, as bread, potatoes, 
&c. With the classes in easy circumstances, however, it is a 
habit to consume a great deal more animal food than is strictly 
necessary or indeed beneficial ; not being required for the pur- 
poses of respiration, and being more than the system is capable 
of assimilating in the form of blood, the nitrogen of this food is 
discharged in the faeces, which are probably therefore much 
richer in this element than that of the working community. 
The solid excrements contain a certain quantity of phosphate 
of lime and of alkaline compounds.* These are at all times small, 
but still smaller when, as in the case of sewage, the soluble 
matters have been washed out by abundant dilution with water. 
I shall revert to this point again ; but in the meanwhile I will 
pass on to the composition of urine. 
* The following analysis of solid human excrement lately made in my labora- 
tory will give a good idea of its value in relation to vegetation. It was collected 
without exposure to any foreign matter. The first column shows the composition 
of the ash — the second that of the dried excrement. 
Analysis of Dried Human Flecks. 
Composition of 
the Ash. 
Composition of 
the Dried 
Excrement. 
88 
52 
12 
79 
1 
48 
4 
66 
0 
54 
14 
98 
1 
72 
13 
48 
1 
55 
37 
17 
4 
27 
2 
10 
0 
24 
10 
40 
1 
19 
2 
83 
0 
31 
None. 
None. 
1 
59 
0 
18 
100 
00 
100 
00 
