OINTMENT OF STAVESACRE. 
405 
cept by ebullition, and ebullition causes decomposition of the solution of per¬ 
chloride. Eighth, the only method of producing pure solution of perchloride of 
iron of officinal strength is to dissolve the anhydrous perchloride in water : say 
5£ ounces added to water, so that the solution shall measure 10 fluid ounces, and 
this solution then diluted to 40 ounces to form a solution of the strength of the 
tincture. 
I beg to recommend the adoption of the last-mentioned process for the prepa¬ 
ration of aqueous solution of perchloride of iron. It is perhaps the most ex¬ 
pensive, requires a considerable amount of manipulative skill, and can only be 
performed in the open air or with appliances for carrying off the chlorine which 
escapes during the operation. Moreover, the great affinity of the salt for 
moisture must always be remembered and counteracted, either by packing it 
in bottles as soon as made, in quantities just sufficient to make half a pint, a 
pint, etc., of solution, or by dissolving it as soon as made (by adding it to 
water, not water to it), and making the solution, rather than the solid, the 
commercial form of the preparation.* All these circumstances are unfavour¬ 
able to the adoption of the process, but it is the only one which will give a pure 
preparation. Finally, I distinctly deprecate the employment of a spirituous so¬ 
lution of perchloride of iron—the so-called tincture. It is true, as I have 
shown, that the tincture suffers no immediate and apparent decomposition if 
excess of acid be present, and there may be those who are of opinion that an 
acid spirituous solution of perchloride of iron is preferable to a mere aqueous 
one of similar strength, because, on keeping, a pleasant odour and flavour are 
produced. With such opinions I have no sympathy whatever. The therapeu¬ 
tist can employ chalybeates, acids, and flavouring bodies if he needs them, but, 
under the definite chemical name of one of them, do not give him all three. The 
art of healing can never make satisfactory progress until compounders of medi¬ 
cines place pure definite preparations in the hands of prescribers. 
ON A NEW FORM OF OINTMENT OF STAYESACRE AND 
ITS APPLICATION IN CERTAIN CUTANEOUS DISEASES. 
BY BALMANNO SQUIRE, M.B., F.L.S. 
In the course of some researches into the pathology and treatment of the 
diseases of the skin, in which I have for some time been engaged, I have 
devoted especial attention to the investigation of one of the severest and most 
intractable of these affections,—one known as Prurigo senilis, or the “old 
man’s itch.” After having carefully examined a large number of cases of this 
disease, I arrived at the conclusion that it was essentially dependent on the 
presence of the pediculus corporis on the surface of the skin, and that all the 
phenomena of the disease were dependent on the irritation set up by the pre¬ 
sence of this parasite. This coloured photograph, which I had taken from a 
case of Prurigo senilis lately under my care, conveys a fair idea of the general 
appearance presented by this disease. Up to that time Prurigo senilis had been 
supposed to be dependent, in some cases, on derangements of the digestive 
organs, in others, on disordered innervation of the skin. In such instances of 
the disease as had been noticed to be accompanied by the pediculus corporis, 
this parasite was supposed to be an accidental complication, in no way concerned 
* This readiness to absorb moisture is greatly influenced by the state of aggregation. In 
the condition of powder or single crystals it certainly does take up water most greedily. 
But if after manufacture it be removed in lumps or masses of crystals, so that as little 
surface is exposed as possible, the rate of absorption is much reduced. 900 grains placed 
in an open wide-mouth bottle on a damp day only absorbed three grains ot water in an 
hour. This amount was, however, sufficient to make the lumps look wot and spoil their 
iridescent appearance. 
