fined and separated, is received into the numerous Orifices of the first lacteal Veins, opening into the faid Inteftines; by these it is conveyed to, and ftrained through the Glands of the Mefentery; whence it is received by a fecond Sort of lacteal Veins, and carried to the Bafon, called the receptaculum Chyli; where being duly impregnated with the Lymph, from the Lymphæducts there poured into it, it is thence carried upward by the thorack Duct, and emptied into the left fubclavian Vein, where it is mixed with the refluent venal Blood, defcends into the right Ventricle of the Heart, is thence circulated through the Lungs into the left Ventricle, and from thence through all the Parts of the Body: And this is the animal Oeconomy, or ordinary Method by which the Blood is renewed, and Life continued.

A. Pray what is the Blood?

B. It is a vital Stream proceeding from the Fountain of the Heart, and circulating conftantly through the whole Body by the Canals of the Arteries and Veins, Boerhave faith, if it be viewed with a MicroScope, it appears to confist of small red Globules fwimming in a thin tranfparent Serum, and that each Globule is made up af fix leffer ones, which refolved, take upon them the Nature of the Serum, whofe Colours are various. He farther faith, that

Of the Chyle, and Blood.

293

the Mixture, Fluidity, Heat, and Redness of the Blood is owing to, and preferved by the circulatory Motion thereof.

A. Pray what is the Rate of the Blood's Motion through the Body?

B. Each Ventricle of the Heart will contain about an Ounce of Blood; the Heart contracts about 4000 in an Hour; hence there paffeth through the Heart every Hour 4000 Ounces of Blood, which is 250%. Weight. Now an Ounce of Blood is equal in Bulk to 1.659 Inches; and if we suppose the Heart contracts 80 Times in a Minute, then 80 Ounces of Blood will be equal to 132.72 Inches, which paffeth the Heart in one Minute. Now Dr. Keil found the Diameter of the Aorta to be 0.73 Parts of an Inch, and thence its Orifice 0.4187; by which divide 132.72, and the Quotient will be the Length of the Cylinder, or Space through which the Blood will move in a Minute, viz. 316 Inches, or 26 Feet, But, because of the Diaftole of the Heart, which takes up half the Time of a Pulfation, there goes out of the Heart 80 Ounces in a Minutę; whence the Blood's Velocity will be double, or it moves at the Rate of 52 Feet in a Minute.

4. And, pray, is the Velocity through the Trunk, the fame as through all the Branches taken together?

B. No; for the fame ingenious Anatomist found the exact Proportion of the Branches to the Trunk of the Artery to be as 12387 to 10000, and confequently the greatest Velocity of the Blood will be to the leaft, as 5233 to 1; or the Blood moves 5233 Times flower in fome capillary Arteries, than it does in the Aorta. The Blood is received from the Arteries into the Veins, where it still moves flower as it approaches the Heart. Now the Arteries are to the Veins, as 324 to 441; and therefore the Blood moves in the Veins above 7116 Times flower than in the Aorta.

A. What Quantity of Blood do you find to be in the humane Body?

B. You ask a Question very difficult to be answered: At prefent I cannot find any Perfon can certainly tell: Authors determine from 10 to 25 lb. and Dr. Keil reckons the whole Body confifts of near Fluids, the greateft Part of which is Blood.

A. What do the Chymifts find the Blood to confift of?

B. Of much volatile Salt, and Spirits; fome Phlegm and Sulphur; a little Earth; and but little or no fixed Salts: Alcalies diffolve in it, and Acids coagulate it.

A. How are the other Fluids of the Body produced? ..

B. They are all feparated from the Blood in fome Part of the Body or other by the

Glands:

Blood and other Fluids of the Body 295

Glands: Thus the Saliva or Spittle, is secerned by parodital Glands behind the Ears, and maxillary Glands of the Mouth; the Bile is feparated by the Liver; the Milk is ftrained off from the Blood by the Glands of the Breafts; the Lymph is a fermenting Liquid fecerned by the fmall conglobate Glands in feveral Parts; the Semen is fecreted from the Blood by the Tefticles, brought thither through various Circumvolutions and Contortions of the Spermatick Arteries; the Pancreas, or Sweet-bread, also separates a fweet lympid Liquor or Juice, to dilute and refine the Chyle; the Urine is fecerned by the Reins; it contains volatile Salt, Spirit, an oily Sulphur, Phlegm, and Earth; from Urine fermented is diftilled that luminous Matter called Phofphorus, which is either folid or liquid; Phlegm is a mucous vifcid Matter, feparated by the Glands of the Mouth, Nofe, &c. Serum is the aqueous Part of the Blood, which is not difcerned from the Blood it felf in the Body; but taken out, it feparates from the coagulated Blood, by the Action of the Cold; the aqueous Humour of the Eye, fecerned from the arterial Blood in the Veffels of the Eye; the chrystalline and vitreous Humours are improperly fo called, they confifting of an infinite Number of fmall Veffels repleat with circulating Fluids.

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A. Sir, I am under an infinite Obligation to you for taking fo much Pains for Information; yet, as you feem to do it with a great deal of Pleafure, I fhall be bold to ask a few Questions more; and, pray, what do you fay of the Nature of Hair?

B. When we examine the Hairs with a Microscope (faith Dr. Keil) we find they have each a round bulbous Root lying pretty deep in the Skin, and which draw their Nourishment from the furrounding Humours; that each Hair confifts of 5 ог 6 others wrapped up in a common Tegument or Tube: They grow as the Nails do, each Part near the Root thrusting forwards that which is immediately above it; and not by any Liquor running along the Hair in Tubes, as Plants grow. Their different Colours depend on the different Quality and Temperament of the Humours producing them; they serve for the Covering and Ornament of the Body. Mr. Derham gives us the Reprefentation of two Hairs of a Moufe (the most tranfparent of any) the one in Fig. L. where a is its Appearance through a fmali Magnifier; and A as it appears through a large one. Fig. LI. c and D are the fame Views of another Hair, to fhew the different internal Make of the Hair of the fame Animal.

4. Prag what are the Nails ?

B. Qur