80 Miscellaneous. 
the cysts necessary for my researches. This dust examined under 
the microscope presented,—l. particles of mineral matters (espe- 
cially silica) and soot; 2. filaments of cotton, fragments of Diatoms, 
débris of vegetable epidermis, of cellular and ligneous tissue, and of 
simple or septate hairs, glumes and glumellze of Agrostis and Poa, 
pollen-grains (especially of gramineous plants), spores, starch, and 
yeast ; 3. filaments of wool and silk, scales of Lepidopterous insects, 
Acari of various ages and more or less shrivelled, dead individuals of 
Anguillula, large, contracted Rotifera, and, lastly, numerous cysts of 
ciliated Microzoa, especially Colpoda, some shrivelled and dead, others 
capable of resuming active life in contact with water, although at the 
period when I observed them I had already kept the hay which 
furnished me with them for fourteen months. 
« My plan of investigation consisting in subjecting the specimens 
of the dust at my disposal to the action of various temperatures, I 
had a previous question to solve, namely,whether the cysts were so uni- 
formly diffused through the dust that, when the latter was divided 
into portions of the same weight, it might be regarded as certain that 
every one of these portions would contain encysted Microzoa. To 
ascertain this, having divided the dust into portions of 50 centi- 
grammes, I put thirteen of these portions, taken at hazard, into the 
same number of test-glasses, each of which then received 40 cubic 
centimetres of filtered water. In less than two hours these thirteen 
macerations were populated with Colpode. It seemed to me that 
this trial authorized me to assume that all the portions still in my 
possession, if placed in the same conditions as the preceding, would, 
like them, have furnished revivified Colpode ; and I held it as certain 
that if the dust was barren under changed conditions, its sterility 
must be attributed to the conditions in which I should have 
placed it. 
‘In all the following experiments there were used, as in the pre- 
ceding trial, 50 centigrammes of dust, and 40 cubic centimetrestof 
water. The dust and water having been placed in a mattrass for the 
experiments at 212° F., and in a test-tube suspended in a vessel 
full of water for those below 212° F., the mattrass or the tube, con- 
taining a mercurial thermometer, was immediately subjected to the 
action of heat. As soon as the desired calorific effect was produced, 
the tube was removed from the bath, or the mattrass from the fire, 
and, after cooling, the maceration was poured into a test-glass. 
«My experiments were forty-one in number, and in fourteen of 
them the portions of dust were boiled. In the latter, two mattrasses 
were kept at 212° F. for ten minutes, eight were kept at 212° F. for 
five minutes, two were kept at 212° F. for two minutes ; lastly, two 
mattrasses were removed from the fire the moment that temperature 
was attained. All these experiments prove that the encysted Col- 
pode are killed by boiling.”’—Comptes Rendus, December 4, 1865, 
p-. 991. 
