8 
DR. HOSKINS ON THE DECOMPOSITION OF CALCULI, 
“At present,” continues Dr. Prout, “no such class of compounds of a decided 
character are known, or appear likely to be discovered ; yet, as no chemical fact can 
be stated a priori, we know not what remains in store among' the arcana of nature.” 
The conviction I had acquired of the truth of these observations induced me to 
abandon all attempts at positive or direct solution, but rather to try the effect of in- 
direct means, namely those of decomposition and disintegration; as preliminaries to 
solution by some bland fluid, or to mechanical removal, by the injection of a con- 
tinuous stream of liquid through a double current catheter. 
It appeared, hitherto, to have been the object, to act on calculi by single elective 
affinity only ; that is, to dissolve the base before it was disengaged from its associated 
acid. This mode having failed to produce agents sufficiently active on the one hand, 
and mild on the other ; it seemed more in accordance with chemical principles, and 
more likely to effect the desired end, if complex affinity could be brought into play. 
It frequently happens, that reactions occur under the influence of double decompo- 
sition, which are not produced by simple affinity: thus, ammonia alone will not de- 
compose nitrate of lime, though carbonate of ammonia answers the purpose readily. 
The triteness of this example will, I trust, be excused in favour of the aptitude with 
which it illustrates my meaning. 
For the above purpose an agent is required, the base of which shall be so attract- 
ive of the acid of the calculus, as to withdraw it from its allegiance ; whilst the acid 
of the agent unites with the basic ingredients of the calculus, to form with them salts 
of easy solution. 
This view of the subject seems to reveal a class of agents so mild as to come di- 
rectly under Dr. Prout’s category. During their employment, the combined acids 
are set free only in combining proportions, to be neutralized in their nascent state by 
the proper base, and removed out of the sphere of action before they have time, as it were, 
to act upon the animal tissues. Whereas, free acids of sufficient strength to act on the 
concretion, and in sufficient quantity, cannot be prevented from irritating, in a greater 
or less degree, the animal membranes with which they happen to be in contact. 
The facility with which salts of lead decompose the phosphates, a facility which has 
led to their employment as tests of the presence of phosphoric acid, pointed them out 
as agents well-fitted for the present purpose. 
Fragments of phosphatic calculi were accordingly immersed in solutions of neutral 
acetate of lead, of various degrees of concentration, and at different temperatures, but 
without result; even when the assay, reduced to powder, was placed in these fluids and 
viewed with the microscope, no chemical action, however slight, was discernible. I was 
disappointed, but nevertheless induced to try some other combination of the metal. 
Dr. Prout mentions, in his valuable work before cited, that fluids containing malic 
acid possess peculiar powers in arresting the deposition of the phosphates. The same 
gentleman informed me that the solvent powers of the /llchemilla arvensis reside in 
the malic acid which this plant contains, My own experience has unequivocally 
