Note h — BOOK IV.

There is a considerable Difference between Dr. Willis, and Etmuller, viz. Whether the Vesiculæ of the Lungs have any muscular Fibres or not? Etmuller expressly saith, Nullas Fibras musculosas, multo minùs rubicundam Musculorum compagem (sunt enim Vesiculæ albidæ & fere diaphanæ) in ipsis reperiri. ubi supr. c. 6. §. 2. And afterwards, §. 3. Pulmones esse molles flexilesque musculosis fibris ceu propriæ explicationis organis destitutos. But Dr. Willis as expressly alerts they have musculous Fibres, and assigns an excellent Use of them; Cellulæ istæ vesiculares, ut nixus pro expiratione contractivos edant, etiam fibras, utì per Microscopium planè conspicere est, musculares obtinent, ubi supr. §. 16. And in the next §, Ut pro datâ occasione majorem aëris copiam exsufflent, aut materiam extussiendam ejiciant, fibris muscularibus donatæ, sese arctiùs contrahunt, contentaque sua penitùs exterminant. Et enim ordinariæ pectoris Systolæ, quas musculorum relaxationes ex parte efficiunt, aërem forsan totum à Tracheâ & Bronchiis, haud tamen à Vesiculis, quâque vice ejiciunt: propter has (quoties opus erit) inaniendas, & totius Pectoris cavitas plurimùm angustatur, & cellulæ ipsæ vesiculures à propriis fibris constrictis coarctantur.