The phosphate content is expressed in the same manner, while the ratio of phosphate to acidity gives the ratio of excretion of phosphate to acidity.
There is in lead-workers a considerable diminution in the amount of phosphate excreted, and, as has been pointed out by Garrod and others, lead apparently produces alteration in the solubility of the uric acid content of the blood, and may therefore allow of its decomposition. Probably lead as a urate is stored up in the tissues. For further particulars of this method of the estimation of the urine, the reader is referred to “Urologie Pratique et Thérapeutique Nouvelle,” by H. Joulie.
An examination of the fæces of persons suspected of lead poisoning may often give definite results both of the presence of lead and hæmatoporphyrin. If small hæmorrhages have occurred high up in the intestine, the presence of hæmatoporphyrin in the fæces may result. The substance may be easily determined by means of the characteristic absorption bands. A quantity of fæces is taken and extracted with acid alcohol, and the filtrate examined spectroscopically. Urobilin bands are commonly present, and, particularly, where much constipation exists these bands are very well marked. There is no difficulty whatever, however, in distinguishing them from the characteristic bands of acid hæmatoporphyrin.
Examination of the Fæces for Lead.
—The moist method or chemical examination given above is the best one to apply for the determination of lead in the fæces. As has already been pointed out, lead is commonly excreted in the fæces, and, if only about 2 milligrammes per diem are being excreted by the fæces in a lead-worker, the quantity cannot be regarded as indicative of poisoning. One of us (K. W. G.) has at times found as much as 8 to 10 milligrammes of lead excreted in the fæces of persons engaged in a lead factory, and exhibiting no signs or symptoms whatever of lead poisoning. If, however, the quantity of lead in the fæces rises to anything above 6 milligrammes per diem, there is definite evidence of an increased absorption of lead, and if at the same time clinical symptoms be present, suggesting lead poisoning, such a chemical determination is of the first importance.
In estimating the presence of lead in fæces, it may be necessary to deal with the separation of iron, which may be precipitated as phosphate and filtered off, the quantitative estimation being proceeded with in the filtrate.
Lead is much more commonly present in the fæces of lead-workers than in the urine, and it is better to examine the fæces rather than the urine in suspected cases.
REFERENCES.
[ [1] Gautier: Meillère’s Le Saturnisme, p. 74.
[ [2] Marsden and Abram: The Lancet, vol. i., p. 164, 1897.