SECT: IL. 4 ABSORPBENT: VESSELS, 13

with uniform fuccefs, and it is fo eafily made by baftily applying a common lens after the divifion of a vine-ftalk, that I think there can be no errorinit; andit is wonderful that thefe veflels, which are found in the alburnum, and confift of a fpiral line, whether they may properly be called abforbent or umbilical veflels, or confift of both, fhould ever have been fuppofed to be air-vefels.

There is neverthelefs an experiment by Dr. Hales, which would at firft view countenance the aflertion, that vesetables abforb air. He cemented the lower end of a fmall twig of a tree with leaves on it into a glafs tube about four inches long, and fet the other end of the tube an inch deep in water, and obferved in a littletime, that the water rofe an inch in the tube; but this muft happen from the vesetable veflels emptying themfelves by the afcent of their juices, and having rigid coats, and therefore not contraéting, a portion of the air was forced into them by the preflure of the atmofphere, as in the above obfervation on the vine-branch cut horizontally.

This reception of air does not happen to the veflels of animal bo- dies, when they are emptied of their blood, owing to the lefs rigidity of their coats; whence the weight of the atmofpheric air prefles their fides together, and clofes the veflel, inftead of pafling into it.

Tu the fame manner no air would pais into the veflels of the lungs of

animals in refpiration, unlefs the preflure of the atmofphere on their fides was prevented by the aétion of the mufcles, which enlarge the cavity of the thorax by elevating the ribs.

4. There are neverthelefs certain horizontal veflels of large di- ameter, which pafs through the bark of trees to the alburnum, which probably contain air, as they. are apparently empty, I believe, in the hving vegetable; for the bark of trees confifts of longitudinal fibres, which are joined together, and appear to inofculate at certain diftances, and recede from each other between thofe diftances like the mefhes of a net, in which fpaces feveral horizontal apertures are feen to pe- netrate through the bark to the alburnum, according to Malpighi,

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