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greater a&ivity in the foul, in the day than in the flight ; and they are likewife ever greater from the food taken in the day- time, for the palfc is always quicker after eating than before it; after a full meal than after a fpare one ; and after a meal of drier and ftronger food than after a meal of food that is moift- er and weaker. Dr. Bryan Rohinfon, Dill", on the Food and Difcharges of human Bodies, p. 73. Vitality and accenfim of the Blood— Dr. Willis endeavours to fhew, that the blood being animate, this animation or life de- pends on its being kindled ; inafmuch as the common affections of fire and flame belong to the blood, though this vital flame do not appear to fight, by reafon its form is fubordinate to an- other fuperior form, viz. the foul of the animal. Vid. Willis, de Sanguinis Accenftone, ap. ejufd. Exerc. de AfTe£t. Hyft. h Hvpoch. Lond. 1670.4^. Phil. Tranf. N° 57. p. 1178. See the article Biolychnium. Quantity of the Blood — Anatomifts and phyficians have gene- rally determined the quantity of blood in the human body to be- between fifteen and twenty-five pounds weight. D. Keill {hews, from many inftances of profufe hemorrhages, that a confiderable greater quantity muff be allowed, fince otherwife the patient could never have furnifhed, or at leaff not furvived, iuch evacuations; the leaft of which exceeded the whole quan- tity of blood fuppofed by Dr. Moulin in the whole body, and many of them more, almoft double of the Iargeft quantity al- lowed by any. Keill, of Animal Secret, p. 104, feq. In reality, the quantity of blood in the body is very difficult to determine. Bleeding to death, the method ufed by Dr. Mou- lin and others, can never give the eftirnate of its true quantity becaufe no animal can bleed longer than while the great artery is full, which will be longer or {horter as the wounded artery is fmaller or greater; and the aorta muft always be the firft veflel that empties. The moft certain way, in Dr. Keill's opinion, is, by finding what proportion the cavities of the vefTels, of which the whole body is compofed, bear to the thicknefs of the coats. This, in the veins and arteries, may be exactly found ; but, in the other vefTels, we only know th< quantity of fluid they contain, by carefully evaporating as much as poflible. Thus the doctor found the fluids to be to the vcffels, in the arteries as 1.7 to one; in the veins as 15.6 to 1 ; in the bones as 1 to 1 : the leaff. of which proportions fhews the liquors to be one-half of the weight of the body ; and if a cal- culation be made on the proportion of the blood in the arteries to their coats, in a body weighing 160 pounds, there will be found 100 pounds of blood. Keill, of Anim. Secret, p. 89, feq. It. p. 1 eg, feq. <%u'mc. Lex Phyf. Med. p. 53. Some think it probable, that at Icaft two-thirds of the quan- tity of blood contained in an animal body, is continually pairing the capillaries and final! vcffels in the glandular end mufcular parts, which can never be drawn off by any quick difcharge from cutting the large veffels ; fince, in that cafe, the larger vefTels being emptied much farter than they can be fupplicd again from the capillaries, a defect of blood vri\\ foon enfue at the heart, upon which the animal falls into convulfions, and the circulation flops, while far the greater part of the blood muft be fuppofed ftagnating in the fmaller and remoter vefTels. M.rg. Phil. Princ. P. 3. prop. 1. p. 398. I/i/lawwability of the Blood— Mr. Boyle having held a piece of human blood, dried till it was almoft pulverablc, in the flame of a candle, found it would take fire, and afford a flame much like that which excited it, burning with a crackling noife, and here and there melting. But this inflammability much better appeared,when putting together four or five thoroughly kindled coals, he laid on them a piece of dried blood of the bignefs of a fmall nutmeg ; for this yielded a large and very yellow name, and if it were feafonably and warily blown from time to time, as the effluvia degenerated into fmoak, would long continue to yield clear and yellow flames. The fame author having caufed fome blood to be dried till it was reducible to fine powder, took part of the powder, which had palled a fine fearce, and cafting it on the flame of a good candle, the grains, in their quick paflasxe through it, took fire ; and the powder flafhed not with- out noife, as if it had been rofin. Boyle. Phil. Works abridg. T. 3. p. 4+9- Blood, in medicine — The prefcriptions of modern phyficians are Generally founded on fuppofition, that a great fhare of difeafes depend chiefly on the vitiated constitution of the mafs of blood A ; and their cure on reftoring the blood to its natural ftate, to be done partly by evacuants, but more by fpecifics or alterants, fo adapted, as to furnifli certain 2ftive corpufcles proper to ferment, or excite an unufual commotion or agita- tion in the blood, whereby it may be corrected, and enabled to expel or furmount the caufe of the difeafe. But it muft be obferved, that, when the whole mafs of blood is to be altered, the courfe of phyfic muft be continued a long time, by reafon the blood moves flower and flower the farther it moves from a great artery ; confequently it muft be a long time before the whole mafs of blood can he mixt with the alterative medicine. Add, that the circulation of the blood through glands, which receive arteries immediately from any great veflel, being very quick, they may carry off a great proportion of the medicine in a very little time; fo that it is not the taking great quan- tities, but a conftant taking for a confiderable time, that can Suppl. Vol. I.
alter the "mafs of blood c .~[ d Phil. Tranf. N* 23S. p. ior. Boyle, Phil. Work, abridg. T. 3. p. 565. e Keill, of Anim. Secret. &c p. 153, 1^4.]
It has long been a difputed point, whether there be any teal acid fait in the human blood? Boyle f , Drake, and others, hold the negative ; but from what has been already (aid, this appears to be a miftake. Sig. Lancifi e and M. Homberg ll have fufficiently proved the exiifence of an acid in the bloody derived, doubtlefs, from the fea-falt and vegetable acid fo plentifully taken in among our food, and not fo totally de- ftroyed by the aclion of the vifcera, but that it ftill retains its nature. — [ f Boyle, Phil. Work, abridg. T. 3. p. 457. « Phil. Tranf. N° 264. p. 599, feq. * Hift. Acad.
Scienc. an. 1712, p. 58. Mem. p. 352.] See the articles Acid, Salt, &c.
Dr. Willis, and others after him, fuppofed fevers, agues, and feveral other difeafes, the effects of a fermentation of the blood. Other more mechanical writers deny, that the blood, while contained in the veflels of the human body, is capable of any fermentation * : yet Malpighi fecms to allow a perpetual fer- mentation of the blood, for the production of urine k . — [* Boyle, Phil. Work, abridg. T. 3. p. 365. k Junck. Confp. Phyf. tab. 20. p. 306.]
To which may be added divers other morbific conftUutions de- pending on the different ftates and difpofitions of the blood, in refpecr. of quantity, velocity, fluidity, denfity, fcrofity, &c. An excefs in the quantity of blood conrtitutes what we call a plenitude, or plethora ; a defect or want of a competent quan- tity, 2Llcipbc£?nia. Cajl. Lex. Med. p. 452. voc. leiphtzmos. The fymptoms of excefs or defecl:, of an over-repletion or depletion, in the blood-veffeh, are obvious ; but caution muft be ufed not to miftake every occafional flufhino; or tide of the blood to the head for a general plethora of the blood-veiTds, fuch tides and flufhings being very common in cafes where there is yet no blood to fpare. Morg. Phil. Princ. Med, P. 3. prop. 1 . P' 399-
The aequilibrium of the blood is an uniform and proportional diffufion of it through all the parts of the bodv- Any cohfiderable ftimulus, it is known, will derive the blood in large quantities to the ftimulated part, which miift necef- farily break the equilibrium and uniformity of its circulation ; whence congeftions, flagnations, concretions, c5V. of the blood ; and hence it is that a great part of regular practice con- fifts in deriving, rcvulfing, difcuffing, and variouily diredtino- and determining the blood, in order to recover its .x-quilibrium. Nent. Fund. Med. T. 1. P. 2. p. ic, 25, 48, 57, 94, 101, 184, zi8, feq. Junek. Confp. Med. p. 108&&29. Morg. Phi4. Princ. Med. P. 3. pr. r. p. 410.
The arquilibrium of the blood againft any occafional affluxes and refluxes of this fluid, is preferved or reftored, either by raifing and diffusing it when too weak and languid by cardiacs; as faffron, opium, Virginia fnake-root, cSV. or by depreffin^r and repelling it when too much raifed and diffufed ; which is done by the abforbents, coolers, purgatives, acids of all forts, efpecially apples. Morg. lib. cit. P. 3. prop. 3. p. 42c.,
feq.
The morbific excefs or defecl; of the blood's velocity is as re- markable as that of its quantity ; but this cannot be judged from the natural ftate of the pulfe in health, which is different in different conftitutions. 'I he ordinary number of pulfations in a minute is from 70 to So under a ftate of waking and mo- derate heat, and from 80 to 96 during the time of fleep. Morg. lib. cit. P. 3. prop i. p, 309.
The too great heat and vifcidity of the blend is one of its moft generally prevailing morbific conftitutions; efpeciaUv in a coun- try as ours, abounding with all the temptations to, and pro- vifions for, cafe and luxury. '1 his ftate of the blood is brought on generally by drinking too freely hot, fpiritnous, inflam- mable liquors, and feeding plentifully on things, which con- tain a large proportion of volatile oily falts ; as flefh-meat? half-boiled or roafted, eaten in their bloody gravy, and all hot, fpicv, and hiobi-feafoned broths, fauces, and the like. The blood being bv thefe over-heated and rarefied, the ferum is, in confequence, thickened into a fort of jelly, by which means it is rendered unfit for motion, coheres too ftrongly with the craffamentum, and paffes but fiovvly through the lymphatics and fecretory glands. In this ftate, the thicker and more vif- cid parts of the ferum, lodging on the lymphatics and recep- tacles of the glands, gradually obftruct or fill them up. From which obftruction and diminifhed or intercepted circulation of the animal fluids, the heat and vifcidity of the blood ftill in- creafes till the vital flame, raifed too high, produces a fever. This ftate of the blood, and its fymptoms, are aggravated by a fedentary life, or the want of due motion and cxercife; for while the natural motion of the mufcular fibrillar is either not at all, or but little promoted by voluntary action, the glands, and their receptacles, muft be the fooner fluffed up, and the circulation of the lymph, that powerful means by which na- ture continually cools and dilutes the blood, fooner be fufpended. Morg. lib. cit. P. 3. prop. 2. p. 41 1 .
The blood is cooled, diluted, and attenuated by tempcrance,exer-
cife, the u(e of water as beverage.,and otherwife,and by deobftru-
ents, efpecially mercury, in the gentler preparations of it ; as
5 C jethiops
