102 POISONS : THEIR EFFECTS AND DETECTION. [§ 73. 
be supposed that the mass of the blood contains any free sulphuric acid 
during life. The acidity of the blood in the vena cava may be ascribed 
to post-mortem endosmosis, the acid passing through the walls of the 
stomach into the large vessel. 
§ 73. Sulphates. —If the acid swallowed should have been entirely 
neutralised by antidotes, such as chalk, etc., it becomes of the first 
importance to ascertain, as far as possible, by means of a microscopical 
examination, the nature of the food remaining in the stomach, and then 
to calculate the probable contents in sulphates of the food thus known 
to be eaten. It will be found that, with ordinary food, and under 
ordinary circumstances, only small percentages of combined sulphuric 
acid can be present. 
As an example, take the ordinary rations of the soldier, viz. :—12 oz. 
of meat, 24 oz. of bread, 16 oz. of potatoes ; 8 oz. of other vegetables, 
with sugar, salt, tea, coffee, and water. Now, if the whole quantity of 
these substances were eaten at a meal, they would not contain more than 
from 8 to 10 grains (-5 to -6 grm.) of anhydrous sulphuric acid, in the 
form of sulphates. 
So far as the contents of the stomach are concerned, we have only 
to do with sulphates introduced in the food, but when once the food 
passes further along the intestinal canal, circumstances are altered, for 
we have sulphur-holding secretions, which, with ordinary chemical 
methods, yield sulphuric acid. Thus, even in the newly-born infant, 
according to the analyses of Zweifler, the mineral constituents of 
meconium are especially sulphate of lime, with a smaller quantity of 
sulphate of potash. The amount of bile which flows into the whole 
tract of the intestinal canal is estimated at about half a litre in the 
twenty-four hours ; the amount of sulphur found in bile varies from -89 
to 3 per cent., so that in 500 c.c. we might, by oxidising the sulphur, 
obtain from 2-2 to 7-5 grms. of sulphuric anhydride. 
It is therefore certain that large quantities of organic sulphur- 
compounds may be found in the human intestinal canal, for with indi¬ 
viduals who suffer from constipation, the residues of the biliary secretion 
accumulate for many days. Hence, if the analyst searches for sulphates 
in excretal matters, all methods involving destruction of organic sub¬ 
stances, whether by fire or by fluid-oxidising agents, are wrong in 
principle, and there is nothing left save to separate soluble sulphates 
by dialysis, or to precipitate direct out of an aqueous extract. 
Again, sulphate of magnesia is a common medicine, and so is sodic 
sulphate ; a possible medicinal dose of magnesia sulphate might amount 
to 56-7 grms. (2 ozs.), the more usual dose being half that quantity. 
Lastly, among the insane there are found patients who will eat plaster- 
of-Paris, earth, and similar matters, so that, in special cases, a very 
large amount of combined sulphuric acid may be found in the intestinal 
