586 poisons : their effects and detection. [§§ 765, 766. 
The phenyl-arsinic acids are obtained from the urine by extracting with 
ethyl acetate. The ethyl acetate extract is treated with water, and the 
aqueous solution concentrated to a small bulk in an atmosphere of carbon 
dioxide. First the amino compound crystallises out in needles, and, on 
separation of the crystals, addition of alcohol to the mother liquor 
precipitates the hydroxy-phenyl-arsinic acid. The behaviour of 
p-arseno-benzoic acid in the organism has been investigated by repeated 
subcutaneous injections of the compound into a calf ; in this case the 
chief excretory product is p-carboxy-phenyl-arsinic acid, and a smaller 
quantity of hippuro-arsinic acid. 
3-ainino-arseno-benzoic acid, when injected, is excreted partly in the 
form of 3-acetyl-amino-p-benz-arsinic acid. 
§ 765. Antidote and Treatment. —In any case in which there is 
opportunity for immediate treatment, ferric hydrate should be adminis¬ 
tered as an antidote. Ferric hydrate converts the soluble arsenious 
acid into the insoluble ferric arseniate, the ferric oxide being reduced 
to ferrous oxide. It is necessary to use ferric hydrate recently pre¬ 
pared, for if dried it changes into an oxyhydrate, or even if kept under 
water the same change occurs, so that (according to the experiments of 
Messrs T. & H. Smith) after four months the power of the moist mass 
is reduced to one-half, and after five months to one-fourth. 
It is obvious that ferric hydrate is not in the true sense of the word 
an antidote, for it will only act when it comes in contact with the 
arsenious acid ; and, when once the poison has been removed from the 
stomach by absorption into the tissues, the administration of the hydrate 
is absolutely useless. Ferric hydrate may be readily prepared by 
adding strong ammonia to the solution or tincture of ferric chloride, 
found in every medical man’s surgery and in every chemist’s shop, care 
being taken to add no caustic excess of ammonia : the liquid need not 
be filtered, but should be at once administered. With regard to other 
methods of medical treatment, they are simply those suggested by the 
symptoms and well-known effects of the poison. When absorbed, the 
drinking of water in excess cannot but assist its elimination by the 
kidneys. 
§ 766. Is Arsenic a Normal Constituent of the Body ?—Arsenic is 
widely disseminated through the vegetable kingdom. F. Jadin and 
A. Astruc ( J . Pharm. Chim ., 1912) have found minute quantities of 
arsenic in sixty-seven different kinds of vegetables, in amounts varying 
from 8 mgrms. in dates to 26*6 mgrms. per 10,000 grms. in radishes : 
that a portion of this arsenic may be absorbed from time to time in the 
tissues or organs may be reasonably presumed. Gautier has shown that 
such arsenic appears to determine to the thyroid, mammary glands, and 
skin ; he has found up to 0'75 mgrm. in 100 grms. of human thyroid, and 
0 13 mgrm. in 100 grms. of mammary gland; he considers that arsenic 
