VOL. IX.] PHILOSOPHICAL TRANSACTIONS. J 47 



hurting their scabbards, in killing animals, in occasioning very tempestuous 

 winds, &c. 



So much concerning the first treatise. As to the other four, we shall not say 

 much of the two former, viz. of respiration and the rickets, but hasten to make 

 some mention of the two remaining parts, treating of the respiration of a foetus 

 in the womb and the egg, and of muscular motion and the animal spirits. 



Touching the former of these, our author considering with himself, how a 

 foetus can live in the womb without the access of air, and finding the offices 

 hitherto assigned to the umbilical arteries to be ill grounded, scruples not to 

 affirm with the learned Everard, that the said arteries are formed chiefly, if not 

 only, for the use of respiration, declaring, that the blood of the embryo, being 

 conveyed through the umbilical arteries to the placenta uteri, carries to the 

 foetus not only the nutritious juice, but also with it a quantity of the nitro-aerial 

 particles, whereby the blood of the foetus, by its circulation through the umbi- 

 lical vessels, is impregnated just as it is in the vessels of the lungs: whence he 

 would not have that placenta called any more the liver, but the lungs of the 

 womb. And this supplement for respiration he extends to the chicken in 

 an egg, asserting, that the same does, no otherwise than a child in the womb, 

 breathe by the said arteries ; esteeming, that the primogenial liquors of the egg, 

 furnished with a pure aerial substance, being incessantly conveyed through the 

 umbilical vessels to the chick, perform to the same the office not only of nutri- 

 tion, but of respiration also. To' this he adds, that even that gentle warmth, 

 excited in the egg by incubation, may also contribute something, there to supply 

 the defect of respiration ; forasmuch as he supposes to have proved in his treatise 

 of respiration in general, that the Aitro-aerial particles, by the blood's fermenta- 

 tion struck out of the parts of the air, serve animals for respiration; and that, 

 as all heat proceeds, in his opinion, from such nitro-aerial particles put into 

 motion ; so in this case, the heat given by the incubating bird, and received and 

 detained in the albumen, is thence collected by the many small suckers of the 

 umbilical vessels, and so conveyed to the chicken. Upon which ground he 

 undertakes to solve that difficult query, viz. why a foetus after it is born, and 

 yet closed up in its membranes, may yet live for some hours; whereas if, being 

 divested of those skins, it have once taken air into its lungs, it cannot live a 

 moment after without it? which he answers thus; that a foetus born, and yet 

 wrapped close within the membranes, is in a like state, and breathes much after 

 the same manner, as a chick included in an egg. But if, those membranes 

 being pulled away from the foetus, it do, for breathing, with labour contract the 

 muscles of the chest and the midriff, it spends in that muscular labour much 

 more of those nitro-aerial parts than before ; whence there is a greater necessity 



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