Chemistry and agers. 259 
needed no further preparation. We need not follow the detail of ve 
es with chlorine, &c., as the effects were similar to om 
given abov G.C.8 
Biouiyrapiy upon Gilass.—The author a produced photograph 
(Calotype) upon glass plates covered with starch, &c., b 
: ip pte te ' 
oO 
mine (white of egg) afforded far better proofs. This substance, or 
rather the most liquid portion, in which is dissolved the iodid of potassium, 
is spread over the plate and dried at a moderate temperature 
The usual application of the aceto-nitrate of silver renders the albu- 
men insoluble, and not liable, therefore, to be disturbed throughout the 
process. The proofs upon paper are far finer if one or two coats of 
potassium gives a blue color immediately on its application to this paper, 
which is again rendered vie (or rather yellowish) on the contact of 
the silver solution. Hence the silver may be applied by the light of 
the faintest taper with ae certainty, no spot being left untouched— 
we can even measure very nicely the amount of silver solution by the 
manner in which the blue iodid is decolored. Such paper we have 
found to give the clearest proofs and most free from spots. | 
15. Note to a paper on the Chemical Nature of Gelatine, published 
in the American Journal of Jan., ,p- 74; by T. 8S. Hunt, (extract 
from a letter to one of the editors.)—In the January number of this 
Journal, I published a communication, the object of which was to 
prove that gelatine is to be regarded as the amidized species of a body 
identical, in composition, with dextrine. This was supported by a 
comparison of its analysis with a calculated formuia and its metamor- 
phosis by the action of dilute sulphuric acid which converts it into sul- 
P aie of ammonia and glucose or grape sugar. At the same time 
ammonia and dextrine of pa A medical friend has mar 
communicated to me a curious case, nc seems directly to confirm 
this suggestion and deserves to be reco 
person who had for a long time “i the subject i diabetes mel- 
litus, consulted him a few months since in regard to his case. He isa 
young gentleman of scientific and observant habits, at has made his 
disease a subject of special study, marking carefully all its various phases 
and the changes pease in the urine by differences in diet. While 
confined to an exc lusively animal diet, he was recommended by his 
physician, as an agreeable variety, to eat calves-foot jelly. This he 
found, to his surprise, at bat increased the specific gravity of his urine, 
and the secretion of sugar became abundant. The patient was att is 
time using no sugar or Reicrieiie food whatever, and he observed that 
the formation of sugar was invariably consequent on the use of the 
