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The right ventricle sends into the lungs a quantity of blood, equal to 

 that which each contraction of the left ventricle propels into the aorta, 

 and it is not necessary to adopt the opinion of M. Kruger, that each con- 

 traction of the heart sends into the lungs, and into the rest of the body an 

 equal quantity of blood, for, in that case, the circulation would have 

 been much slower, the length of the lungs being much shorter than the 

 whole body. Nor need we say, with Boerhaave, that this circulation is 

 much more rapid, because the same quantity of blood returns by the 

 extremities of the pulmonary artery, and of all the other arteries of the 

 body. 



The extensiou of the pulmonary tissue, the straightening of its vessels 

 are, no doubt, favourable to the circulation of the blood, but if the ad- 

 mission of air did not answer a different purpose, the circulation would 

 not be indispensably necessary. The blood flows from the right into the 

 left cavities of the heart, notwithstanding the collapse of the lungs and 

 the creases of their vessels. The air which penetrates, at all times, into 

 the lungs, supports their tissue and the vessels which are distributed to 

 it, so that even during expiration, the vessels are much less creased, than 

 has been imagined by several physiologists. But the changes produced 

 by the contact of the atmosphere; renovate this fluid, and fit it to re-excite 

 and keep up the action of all the organs, which require to be stimulated* 

 by arterial blood. If you make a living animal breathe de-oxygenated 

 air, the blood undergoes no change by its pulmonary circulation; the 

 left cavities of the heart are no longer duly irritated by this fluid, which 

 preserves all its ven.ous qualities; their action becomes languid, and 

 with it that of all the organs; and in a little while, it ceases altogether. 

 It is revived by introducing pure air, through a tube fitted to the trachea; 

 ail the parts seem to awake out of a sort of lethongic sleep; in which 

 they are again immersed, by depriving the lungs anew of the vital air. 



The chyle, mixed in great quantity with the venous blood, undergoes, 

 in its passage through the heart and the sanguineous system, a more vio- 

 lent agitation ; its molecules are struck together, break on each other, 

 and, thus attenuated, become more perfectly intermingled: in its passage 

 through the lungs, a great part of this recrementitious fluid is deposited 

 by a sort of internal perspiration, in the parenchymatous substance of 

 these viscera. Oxy dated by the contact of tne air, re-absorbed by a mul- 

 titude of inhalent vessels, it is carried into the bronchial glands, which 

 are found blackened by what it there deposits of carbonic and fuliginous 

 matter. Purified by this elaboration, it returns into the thoracic duct, 

 which pours it into the subclavian vein, whence it soon returns to the 

 lungs, to be there anew subjected to the action of the atmosphere ; so 



* Some, hypercritics very strenuously object to the use of the term stimulation as ap- 

 plied to the 'action of the blood on the heart, and they urge that all stimulants disturb 

 or irritate, and, therefore, are unnatural, which the blood certainly is not. Neverthe- 

 less, the blood is the natural stimulus or excitant of the heart, and does in reality irritate 

 or disturb that organ under peculiar circumstances. It is true that the word stimulus 

 has by common custom a more enlarged meaning than its bare etymology would allow. 

 To those who are such sticklers for etymology as fixing significations, we may address 

 the following pertinent observation of the illustrious HARVKY . " De verbi autem ety- 

 mologia, non sum hie magnopere sollicitus ; neque enim pro jure pbilosophico esse cre- 

 dimus, ex verborum significatione illiquid de naturss opeiibus statuere, aut disceptationes 

 \medicas} vocare ad tribunal grammatical. Non est nempc tarn quaerendum quid vo- 

 cabuls. proprie significent, quam (VCOMOKO VTJLOO rsunpENTrn.' 1 ' Kp. 1. 



