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the whole then, the globules of the firft order ate made up of fix globules ofthefecond, thefe of fix of the third, thefe of fix of the fourth, thefe of fix of the fifth order, and fo on. And accordingly, we find the globules of the higher orders may be broken down into their compounded particles. 1 hat the blood, in fome cafes, might be turned into ferum, was ob- ferved by Ariftotle Nor did fuch a. change of the blood efcape the obfervation of the accurate Dr. Harvey s.— [* Vid. PhiloC Tranf. N° 102. p. 23. Item, N° 106. p. 122. and' p. 129. It. N" 109. p. 380. It. N° 165. p- 7S8. feq It. N° 263. p. 552. It. N° 380. p. 436. e Med. EfT Edinb. T. 2. p. 74. f Id. ibid. p. 76. b Id. ibid. p. 77.] Dr. Martine has alfo given us fome computations of the dia- meters, magnitudes, weights, &c. of the] globules of the blond. The doctor's computation of the diameter of a red glo- bule agrees with Lcwcnhoeck's and Dr. Jurln's, being about tttb of an inch.

The blood, as already obferved, is compofed of globules of dif- ferent orders and magnitudes. The diameters of thofe of the tenth order are eilimatcd at lefs than +ox-o5c of an inch. See Medic. Efl". ibid, or Abridg. Vol. r. p-256. feq. Elements of 'the Blood, according to the antic nts, were,

j. The «V«, or the red part, which they confidercd as the true and proper blood. 2* The <p^f*a, or ferum. 3. Bile. And, 4. MiAay^oXta, or atra bilis : and from hence did the doctrine of temperaments take its origin. Martine, in Medic. Eff. Edinb. T. 2. Art. 7. §. 2. p. 68.

The fcveral temperaments, fanguine, choleric, phlegmatic, bV. took their denominations from the conflituent parts of the blood, as abounding more or lefs in one, or other of thefe elements. Martine, loc. cit. §, 6. p. 82. feq. 1 The elements of the blood, according to the chemifts, are wa- ter, fuiphur, fait and earth.. Vid. Martine, ibid. §. 3. p. 70. feq.

The fibres in the blood, ftrcnuoufly affected by Malpighi, are not to be found in its natural ftate. If they were, they muft difturb the circulation. Their appearance feems to be entirely owing to a fubfequent preparation of extravafated blood, vvhofe vifcid parts, by the heat of warm water, and conqtiafllitions. or fuch artifice, run together into new forms. Martine, ir Medic. Eff. Edinb. Vol. 2. Art. 7.

According to Dr. Martine, the blood being unity, and con- fiding of 4873 grains, its elements are in the following pro- portions.

Water

gr. 4086

1

Oil

— —

333

Salt

—

190

Earth

65

Air

171

The denfitv of the blood is commonly examined, when it is expofed to cold air; but as the blood thus expofed muft differ from what it is, when, circulating in the veflels of the animal, its real and natural denfity fhould be invefti- gated in a live ftate. We know that all bodies are con- denfed by cold, and expanded by heat ; therefore cold blood is fpeciflcally heavier than the warm fluids circulating in the vef- fels of a living animal ; but the difference is not eafy to deter- mine. Dr. Martine, from his observations and experiments, concludes the real denfitles of water and blood to be in thefe proportions.

Water in a temperate degree of heat — ■ - freezing ■.

1000 IC03

of the heat of human blood in the body — ggo

Blood of the heat of temperate air 1056

— — in its natural living ftate — ■ 1045*

Hence we may determine the weight of a given hulk of blood, which has not been hitherto done fo accurately as it deferves. The doctor from his experiments concludes* that a cubic inch of rain water, weighing 253' grains, a cubic inch of warm blood will be equal to 264^.- grains ; and an ounce of blood will be 1,813 inches. An averdupois ounce is found to weigh 437*" grains, and ia therefore in water equal to 1,727 inches; and 1,6526 inches of warm blood, See Medic. Eff Edinb. Vol. 2. Art. 7.

The fame author makes the denfity of cold ferum 1032, that of rain water being 1 000. And the ferum reduced to the heat of HveMwd? 10215, or 1022. Dr. Jurin found the denfity of the crafiamentum 1084. but this varies confidcrably indiffe- rent fubjects, and Dr. Martine, at a medium, found it 1080 j and he thinks the true denfity of a red globule circulating in the bloodoi a living man to be 1093. The reafon for this increafe of denfity is, that two thirds of the crafiamentum are taken up by red globules, and the other third by ferum. TT"S differs

fomcthing from Dr. Turin's computation. See Medic. Eff ibid. & Phil. Tranf. N°36i.

If the red part of the blood bears too great a proportion to the ferum, which is the cafe of athletic perfons,- and others who do not take a fufficient quantity of drink with their meat, the fault may he corrected by leffening the meat, or by' increafhig their drink. Dr. Bryan Robinfon tells us of a young man, who not having for a confiderabletime drank with his meat, had a very florid complexion, and fcorbutic erup- tion all over his body, arguments of too great a proportion of the red part of the blood to the ferum, was freed from his dif- orderby drinking with his meat, without any farther remedy. Diff. on the food and difcharge of human bodies, p. 65. In the beginning of fevers, the proportion of the red part of the blood to the ferum is greater, and at the end of them lefs, than it is in health. The change of this proportion is owing, to perfons under this diforder living wholly on drink and li- quid nourifhment. And bodies loaded with ferous moifture, an argument of too fmall a proportion of the red part of the blood to the ferum, have been freed from their load, by ab- ffaining wholly from drink.

There are other caufes befides the hare quantities of meat and drink, which vary the proportion of the red part of the blood to the ferum ; for this proportion is greater in country people than in citizens, in perfons who ufe excrcife than in perfons who are inactive, and in perfons who live upon flefli meats, and fermented liquors, than in perfons who live upon vegeta- bles and water. In fhort, this proportion is increafed by things which dry the body, and ftrcngthen the fibres, and leflened by things of a contrary nature.

Too great a proportion of the red part of the blood to the ferum, renders bodies fubject to inflammatory fevers on taking cold. Ibid. p. 66, feq.

When extravafated blood is left to itfelf, the red globules run- forcibly together, and fquceze out the intervening ferum in fome animals with a greater, in others with a lefs force; which; is a pr,oof r that thefe globules are endowed with an attractive power. This force in deer's blood is fo weak, that it fcarcely coagulates into a firm crafiamentum. On the contrary, in fome great and ftrong bcafts, it becomes a tough, and alraoft indif- foluble mafs ; fo that the blood of bulls was frequently drank by the antients, as a moft effectual poifon. See Herod, in. 15. Plin. Hill. Nat. xi. 33. xx. 9. xxin. 7. Plutarch, in vit. Themift. See Extravasated.

Mr. le Cat thinks, that the blood is detained in its fluid ftate by a cauftic fluid, and that this forms the red globules. But then it needs the affiftance of the animal fluid, which is the principle that preferves all from corruption, and to which we owe our fen Cation and motion. Med. Eff Edinb. Abrid. vol. 2. p. 481. See Sensitive Jluid.

Colour of the Blood varies according to the rircumftances of the perfbn y a blacknels arifes in it from a deficiency of the ferum ; and a palcnefs, from a too great abundance of it. It will always be found, that when globules cohere together m too great a number, they give a black appearance ; and when this is found to be the ftate of the blood, the means of diluting it fhould always be attempted. When Mr. Lewenhoeck found his blood too deep-coloured, his method always was to drink four dimes of coffee in the morning in dead of two, and fix dimes of tea in the afternoon inftead of three. Thefe he al- ways drank as hot as poflible, and did not return to his ufual flint, till he found the globules of his blood grow paler.

Circulation of the Blood, viewed with the microfcope in tlie tail of a fmall eel, affords one very beautiful phenomenon ; that is, when the blood has palled in feveral channels to the end of the lait bone ; it there forms one fimple channel, in which there feems to be a valve ; and the progreffive motion of the blood is different there from what it is in other places, the whole mafs coming to a fudden ftop, yet never getting at all back, and then advancing forward in a ftrait line with violence ; and thefe fucceflive progrelles were fo quick, that one could fcarce have time to pronounce a fyllable between one and the other of them. The veflels alfo about the head in a very fmall eel fhew very beautifully this circulation; and the mo- tion of the heart is cafily feen. See Circulation.

Motion of the Blood is either progreffive or inteftine. The pro- greffive motion is Its courfe or circulation from the heart by the arteries to the extreme parts, and thence by the veins to the heart a ; which is differently performed in adults from what it is in a fcetus *.— [ a Vid. Hift. Acad. Scienc. ann. 1718. p. 21. It. Mem. p. 2810. b Vid. Nent. Fund. Med. tab. 1. T. [. p. 7. Mem. Acad. Scienc. ann. 1708. p. 240.] See Circulation and Foetus.

The propulfion of the blood, or the impetus wherewith it is. driven along its courfe to the remoteft capillaries, is owing to the contraction of the left ventricle of the heart and that of the arteries ; regurgitation of the blood being prevented by the figmoid valves. Hift. Acad. Scienc. an. 1713. p. 29. This Is great enough in fome animals to raife the blood fix, fe- ven, or eight feet high from the orifice it fpins out at ; which, however, is far exceeded by that of the fap of a vine in bleed- ing-time, which will fometimes rife upwards of forty feet high. Hales, Veget. Stat. c. 3. Phil. Tranf. N° 398. p. 274. The heat and raotion of the blood are always greater from a

greater.