BIO

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a fub-phofphat of iron. Cauftic alkalies added to•the former pliofphat only partially decompofeit, and by taking away a portion of the phof-phoric acid, reduce the remainder to the ftateof fub-phtilphat of iron. This too agrees withthe habitudes of fome of the other phofphatswith regard to partial decompofition. Now asthe blood always contains an excefs of foda,the abovementioned chemifts ingenioufly explainthereby the red colour of the blood, by fup-pofing the phofphat of iron to be conftantlykept by the foda in the ftate of fub-phofphat.They likewife endeavoured with fuccefs to pro-duce a kind of artificial blood, as far as colourwas concerned, by diffolving a fub-phofphat ofiron in white of egg or in ferum of blood, whichwas very readily effected even in the cold, andgave a blood-red fluid, the colour of which wasfurther heightened by a fmall admixture ofcauftic fixed alkali.

The craflamentum of blood therefore, fromwhat has preceded, is found to confift chiefly ofthe fibrin, and a phofphat of iron mixed inti-mately with a portion of ferum into a peculiarred fubftance, which under the microfcopeexhibits an appearance of a vaft multitude ofglobules, of a determinate fhape and fize.

2. The ferum of blood is the clear yellowliquor in which the craflamentum floats afterit is coagulated. Its tafte is fomewhat falineand peculiar, when agitated it froths readilyand has a clammy feel to the fingers. Its fpecificgravity is about 1.027, according to Jurin andMufchenbroek. It immediately turns fyrup ofviolets green, and gives other marks of an excefsof alkali which analyfis confirms. This alkaliis foda. It readily unites with water, but bylarge dilution it turns milky.

When ferum is heated to 160 0 or upwards,a large quantity of a whitifh fubftance coagu-lates, fo as aimoft entirely to folidify the ferum,but on cutting up the coagulum a confiderableproportion of a thinner watery liquid oozes out,which is called by phyfiologifts the ferofity.The coagulated mafs, if gently heated for a littletime, becomes hard, brittle and horny. It agreesfo precifely in every chemical character withthe white of egg and the other fubftances ofthis fpecies, that it is juftly reckoned as pureAlbumen, the properties of which are defcribedunder that article. If this albumen is calcinedwith a ftrong heat it bums with the ufual pro-ducts, and leaves in the coal a faline mixtureconfifting of muriat, phofphat, and carbonat offoda. Thefe falts are foreign to what may be

confidered as the true conftituents of albumen,and muft therefore be added to the lift of com-ponent parts of blood, except the latter, whichinftead of a carbonat muft be confidered asnaturally pure foda, having been doubtlefs car-bonated during the calcination.

Alcohol added to ferum alfo coagulates thealbumen, as it does any other albuminousliquid. Acids do the fame, the more com-pleatly as the acid is more concentrated, andafter coagulating the albumen they unite with,the excefs of foda, forming the rcipeftive faltswith this alkaline bafis.

Another fubftance held in folution in theferum is gelatin. This is obtained by boilingdiluted ferum to coagulate the albumen, andthen feparating the clear liquid or ferofity,evaporating it flowly nearly to drynefs, andcooling. It will then appear as a ftift' gelatinousmafs, poflefling all the properties of gelatin,though mixed with all the lalts of the ferum.Parmentier and Deyeux g in their very elaborateanalyfis of blood, obtained the gelatin in a lefsexceptionable way. They heated fome pureferum in a water bath, whereby the albumenwas coagulated, and then inftead of feparatingthe folid from the fluid part, they continued theevaporation half an hour longer. The refiduewas white and cellular underneath, and eachof thefe fmall cells contained a thick yellowtranfparent fubftance, which refembled in itsproperties the pureft glue. The gelatin is onlyfound in the ferum, and was obferved by thefechemifts to vary confiderably in proportion indifferent perfons and animals, without beingobvioufly connected with any ftate of health ordifeafe, or any kind of food or habitudes of theanimal that furnifhed it.

Sulphur is another ingredient in blood, andis found in a minute quantity in the coagulatedalbumen, being indicated by blackening filverand producing the odour of fulphuretted hy-drogen with acids. If the albumen of blood isheated in a filver veffel, the latter will becomeof a deep black'ifh-brown, in the fame way thatfulphur -tarnifhes polifhed filver. If nitratedfilver be triturated with albumen, and the mix-ture .digeited for fome time in a moderate heat,a black precipitate of fulphuretted filver is pro-duced, from which the fulphur might readilybe extracted. A fimilar indication of fulphuris fhewn by the whites of boiled eggs, whichevery one knows will blacken a filver fpoonaimoft immediately on touching it.

Laftly, the ferofity or aqueous portion of th$

* Journ. de Phyf.