$66 OXYGENATION Sect. XXXVIII. i. i. 



SECT. XXXVIII. 



SF THE OXYGENATION OF THE BLOOD IN THE LUNGS, AND 



IN THE PLACENTA. 



L Blood abforbs oxygene from the air, whence phofphoric acid, changes 

 its colour, gives out heat, and fomc phlogifiic material, and acquires 

 an ethereal fpirit, which is dffipated in fibrvis motion. II. The 

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

 the blood f rem air, from water, by lungs, by gills, by the placenta ,• 

 neceffity of this oxygenation to quadrupeds, to fJJj, to the fetus in 

 vtero. Placental vejfels inferted into the arteries of the mother. 

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

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

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

 found in the efophagus and flomach, and forms the meconium, 

 Aionflrous births without heads, ^uejlion of Dr. Harvey. 



I. From the recent difcoveries of many ingenious philofo* 

 phers it appears, that during refpiration the blood imbibes the 

 Tital 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 phlogiltic 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 phlogifiic 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 conflant 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 biufh 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 friction of the particles of the blood againft the 



fides 



