SICT. XXXVIII i. OXYGENATION O? BLOOD. 535 



That the blood requires fomething from the air, 

 which is immediately neceffary to life, appears from 

 an experiment of Dr. Hare (Philof.Tranfadt. abridg- 

 ed, Vol. III. p. 239.) who found, " that birds, mice, 

 &c. would live as long again in a veffel, where he had 

 crowded in double the quantity of air by a condenf- 

 ing engine, than they did when confined in air of 

 the common denfity." Whereas if fome kind of 

 deleterious vapour only was exhaled from the blood 

 in refpiration ; the air, when condenfed into half 

 ks compafs, could not be fuppofed to receive fcf 

 much of it. 



II. Sir Edward Hulfe, a phyfician of reputation 

 at the beginning of the prefent century, was of 

 opinion, that the placenta was a refpiratory organ, 

 like the gills of nfh, and not an organ to fupply 

 nutriment to the foetus ; as mentioned in Derham's 

 Phyfico-theology. Many other phyficians feem to 

 have efpoufed the fame opinion, as noticed by Ha!* 

 ler. Elem. Phyfiologise, T. r. Dr. Gipfon publifhed 

 a defence of this theory in the Medical Eflays of 

 Edinburgh, Vol. I. and II. which doctrine is there 

 controverted at large by the late Alexander Monro, 

 and fince that time the general opinion has been, 

 that the placenta is an organ of nutrition only, 

 owing perhaps ra-ther to the authority of fo great a 

 name, than to the validity of the arguments adduced 

 in its fupport. The fubjeft has lately been refum-ed 

 by Dr. James Jeffray, and by Dr. Forefter French-, 

 in their inaugural diflertations at Edinburgh and at 

 Cambridge ; who have defended the contrary opi- 

 nion in an able and ingenious manner ; and from 

 -whofe Thefes I have extracted many of the follow- 

 ing remarks* 



Firft, by the late difcoveries of Dr. Prieftley, M. 

 Lavoifier, and other philofophers, it appears, that 

 the bafis of atmofpherical air, called oxygene, rs- 

 received by the blood through the membranes of 



the 



