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With respect to the conversion of chyle into blood, the scope of its 

 seat is no less ample than the whole vascular system. These additional 

 questions arise upon it: 1st, is the conversion produced by a relation 

 which chyle has with the properties of the arteries? or, 2nd, is it by 

 a relation with properties of the veins? or, 3rd, is it by a relation 

 with properties of the lungs, superadded to their atmospherical 

 function? or, 4th, is it by a relation with the secerning extremities 

 of the arteries? or, 5th, if with these extremities, is it common to all, 

 or does it belong only to those of a particular seat? or, 6th, is there 

 any other viscus in which the conversion takes place? or, 7th, is the 

 conversion of chyle into blood an effect produced in no single seat, 

 in no one order of vessels, but a result of all the processes which 

 occur in the vascular system? and, 8th, if not the result of all, but 

 of some or many of the processes, what are the seats of those pro- 

 cesses r and of what kind are they? This latter question will admit 

 the application of the analysis which has been many times ske'tched. 



11. Until it shall be shewn that the conversion of chyle into 

 blood takes place in the lungs, there is nothing more to be said of 

 these organs; there being no proof that they possess any function in 

 addition to that of converting venous into arterial blood. X er > e ven 

 in this simple matter, there is something for the chymists to settle, 

 the minute inquiry into which might furnish those proofs which we 

 have just said were wanting. We require to be informed satisfac- 

 torily, whether the same integral changes occur in blood removed 

 from the body as those which take place in the lungs. To answer 

 this, they must extend their analyses: whether the same gases arc 

 evolved? whether the same are imbibed ? whether the same constitu- 

 tion succeeds among the other components of blood, i.e. whether the 

 constituent properties of blood will preserve in every respect the same 

 relations? whether the exhalations are of a similar quality? From 

 the results of inquiry upon these topics (which may be still further 

 multipled) it is to be inferred whether the relation of blood in the lungs 

 is wholly of the atmospherical kind. If it is not, then the properties 

 of life come to be considered, as whether of the assimilating, or of 

 the regular dependent, or of the occasional kind, in agreement with 

 those indications for an analysis which have been before mentioned. 



12. The mechanical phenomena of respiration have been in- 

 vestigated with more success than those which respect some other 

 relations of life. The lungs are considered as passive in the 

 acts of respiration. Their soft and cellular texture is compressed by 

 the diaphragm, &c. and the air thus forced out of them, the capacity 

 of the thorax being at this time diminished: this is the act of expi- 

 ration. In inspiration, the air enters the cells of the lungs, the 

 diaphragm sinks, and the capacity of the chest is increased : these 

 acts are alternated, and they constitute mechanical respiration. 

 Thus far the matter is very clear. Yet though the supposition is 

 tolerably current that little or nothing remains to be added to our 

 information respecting this process (its dependence upon the brain 



