818 
DE. SMITH ON THE ELIMINATION 
other really performed hard labour; and it will be observed that there were many 
differences in the results obtained from them. Both classes had a similar and sub- 
stantial dietary, but there were certain personal differences. Thus, the weavers of 
cocoa-matting- in the -wide loom, when compared with the Tailors, were older, taller, 
heavier, and broader. They ate more bread, milk, and water. They lost weight, 
whilst the Tailors gained weight. They emitted more urine, urea, chloride of sodium, 
and faeces with their contained nitrogen. They exhibited much less diminution in the 
amount of urea evolved on the Sunday, and a little less urea to body-weight. 
It is not possible to compare the results of this inquu-y very closely with those 
already described in reference to Coldbath Fields, since the conditions in each set of 
experiments were not identical. At Coldbath Fields the quantity of bread and water 
was rigidly fixed, whilst at Wakefield there were daily variations according to the 
desires of the prisoners. The quantity of bread eaten was greater at Wakefield than 
at Coldbath Fields, and would so far increase the amount of produced^ whilst the 
variable quantity of water taken from day to day would at the same gaol vary the 
elimination of that product. Yet these causes of variation have only a certain value ; 
and upon the whole it wiU be seen that there is a very close correspondence between 
the excretions of the Weavers at Wakefield and those who worked the treadwheel at 
Coldbath Fields. 
The weight of the men at Wakefield was greater than that of the prisoners at Cold- 
bath Fields ; the quantity of urine and of fluid drank was less, and that of urea was 
greater ; but the proportion of urea to body-weight was very nearly the same at the two 
prisons. In both there was more urea evolved on days of hard labour, and less on 
Sunday. There was less chloride of sodium evolved, as there was less supplied in the 
food. The weight of the fgeces and the contained nitrogen was the same at both 
places.] 
8. Certain relations of TJrea to Food. 
All observers have found that the amount of urea varied with the food taken, and was 
the greatest with that food which yielded the most nitrogen — as, for example, albumen 
and gelatine. This has been well established by Lehmann, Biddee and Schmidt, and 
Lawes and Gilbeet, and many others of the best repute; and there was usually a 
correspondence between the increase in the nitrogen supplied and excreted, if the 
body-weight remained the same. 
I have in former parts of this paper referred to the influence which food exerts upon 
the excretion of urea, and particularly in the effect of absence of food over the hourly 
rate of excretion, and the effect of increased food on Sundays. I propose now to show 
the effect of food taken at a late hour, and of unusual kind and quantity, as occurred on 
various occasions at dinner and evening parties during the year, and then to refer to a 
few special experiments on foods. 
