3 66 OXYGENATION SECT. XXXVIII. i. 



SECT. XXXVIIL 



OF THE OXYGENATION OF THE BLOOD IN THE LUNGSj AND 

 IN THE PLACENTA. 



I. Blood abforbs oxygene from the air ^ whence phofphoric acid^changes 

 its colour, gives out heat^ andfome phlogiflic material, and acquires 

 an ethereal fpirit, which is diffipated in fibrous motion. II. The 

 placenta is a pulmonary organ like the gills offifh. Oxygenation of 

 the blood from air , from water , by lungs , by gills > by the placenta ; 

 tiectffity of this oxygen ation to quadrupeds, to fi/h y to the fetus in 

 utero. Placenta] veffe/s inferted into the arteries of the mother. 

 Ufe of cotyledons in cows. Why quadrupeds have not fanguifer- 

 ens lochia, Oxygenation of the chick in the egg, of feeds. III. 

 The liquor amnii is not excrementitious. It is nutritious. It is 

 found in the e/bphagus and Jlomach, and forms the meconium. 

 Monjlrous births without heads, ^ueflion of Dr. Harvey* 



I FROM the recent difcoveries of many ingenious philofo- 

 phers it appears, that during refpiration the blood imbibes the 

 vital part of the air, called oxygene, through the membranes of 

 the lungs ; and that hence refpiration may be aptly compared to 

 a flow combuftion. As in combuftion the oxygene of the at- 

 mofphere unites with fome phlogiftic or inflammable body, and 

 forms an acid, as in the production of vitriolic acid from fulphur, 

 or carbonic acid from charcoal, giving out at the fame time a 

 quantity of the matter of heat ; fo in refpiration the oxygene of 

 the air unites with the phlogiftic part of the blood, and proba- 

 bly produces phofphoric or animal acid, changing the colour of 

 the blood from a dark to a bright red ; and probably fome of the 

 matter of heat is at the fame time given out according to the 

 theory of Dr. Crawford. But as the evolution of heat attends 

 almoft all chemical combinations, it is probable, that it alfo at- 

 tends the fecretions of the various fluids from the blood ; and 

 that the conftant combinations or productions of new fluids by- 

 means of the glands conftitute the more general fource of ani- 

 mal heat ; this feems evinced by the univerfal evolution of the 

 matter of heat in the blufh of fhame or of anger ; in which at 

 the fame time an increafed fecretion of the perfpirable matter 

 occurs ; and the partial evolution of it from topical inflamma- 

 tions, as in gout or rheumatifm, in which there is a fecretion of 

 new blood-veflels. 



Some medical philofophers have afcribed the heat of animal 

 bodies to the friftion of the particles of the blood againft the 



fides 



