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500 PHILOSOPHICAL TRANSACTIONS. [aNNO I67O. 



trying what it would do in respiration ; and the rather, because I presumed it 

 might prove an experiment of good use, if vve should discover, that by a gra- 

 dual accustomance an animal may be brought to live either in a much thinner 

 air, or much longer in the same air, than at first he could. But in regard that to 

 make such a trial perspicuously enough, the opacity of the bladder made use of 

 in the former title, was like to be an impediment, I devised another way to ob- 

 viate this inconvenience, which may, I hope, be competently understood by the 

 heedful perusal of the following trials. 



Exp. I. — ^We included in a round phial with a wide neck, (the \^hole glass be- 

 ing capable of containing about eight ounces of water) a young and small mouse, 

 and then tied strongly upon the upper part of the glass's neck a fine thin blad- 

 der, out of which the air had been carefully expressed, and then conveyed this 

 fantastical vessel into a middle sized receiver, in which we also placed a mer- 

 curial gauge. This done, the air was by degrees pumped out, till it appeared 

 by the gauge that there remained but a fourth part in the external receiver, 

 whereupon the air in the internal receiver expanding itself, appeared to have 

 blown the bladder almost half full, and the mouse seeming very ill at ease by his 

 leaping, and otherwise endeavouring to pass out at the neck of his uneasy pri- 

 son, we, for fear the over thin air would dispatch him, let the air flow into the 

 external receiver, whereby the bladder being compressed, and the air in the 

 phial reduced to its former density, the little animal quickly recovered. 



Exp. II. — A while after, without removing the bladder, the experiment was 

 repeated, and the air by the help of the gauge was reduced to its former degree 

 of rarefaction, and the mouse, after some fruitless endeavours to get out of the 

 glass, was kept in that thin air for full four minutes, at the end of which he ap- 

 peared so sick, that to prevent his dying immediately, we removed the external, 

 and took out the internal receiver. Whereupon, though he recovered, yet it 

 was not without much difficulty, being unable to stand any longer upon his feet, 

 and for a great while after continued trembling. 



Exp. III. — But having suffered him to rest a reasonable space of time, pre- 

 suming that assuefaction had accustomed him to greater hardships, we conveyed 

 him again into the external receiver, and having brought the air to the former 

 degree of expansion, we were able to keep him there for a full quarter of an 

 hour, though the external receiver did not considerably leak, as appeared both 

 by the mercurial gauge, and by the continuing distension of the bladder. And 

 it is worth noting, that till near the latter end of the quarter of an hour, not only 

 the animal scarcely appeared distressed, remaining still very quiet, but which 

 is more, whereas when he was put in the tremblings formerly mentioned were 

 yet upon him, and continued so for some time; yet afterwards, in spite of the 



