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COMPOSITION OF COTTON OTL-CAKE. 
solution of nitrate of silver. Being shaken together it is 
allowed to rest for some time in a dark place, when, if much 
rape oil be present, the lowest layer will assume a brown 
colour, changing at last to a black; but if only a small 
quantity exists, the colour will be a brownish black. 
ACCUMULATION OF ARSENIC IN THE SYSTEM. 
Dr. Kech, having experimented on a horse with arsenic, 
found the poison in the saliva, the blood, the urine and excre¬ 
ment; the largest portion in the last named. He says that 
the elimination of arsenic by the urine takes place very 
slowly, and that it accumulates in the blood. 
GASES EVOLVED DURING THE RESPIRATION OE PLANTS. 
It has been long known that the organs of respiration in 
plants are the leaves, and that by them, under the influence 
of light, the carbon of the carbonic acid inspired becomes 
assimilated, and the oxygen is eliminated. Thus, too, a 
reciprocity is shown to exist between the two grand organic 
kingdoms, so called. M. Boussingault, however, has lately 
instituted a series of experiments, the results of which he 
has embodied in a memoir, presented to the French Academy, 
the concluding paragraph of which contains the following 
inquiries:—“ Is it not curious that, after the lapse of a 
century, it should be established that probably the leaves of 
all plants, and certainly the leaves of aquatic plants, in 
emitting oxygen, which purifies the atmosphere, also gives 
off one of the most deleterious gases known, namely, oxide 
of carbon ? May it not be permitted to infer, that in the 
emanation of this poisonous gas exists one of the causes of 
the unhealthiness of marshy districts ?” 
COMPOSITION OE COTTON OIL-CAKE. 
Mr. F. G. Calvert, F.R.S., gives the following analysis, 
recently made by him, of cotton oil-cake, respecting which 
he says, it will be seen that it closely resembles in composi¬ 
tion, linseed, rape, and all other oil-cakes used by agricul¬ 
turists : 
