B L O

BL O

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portion to be similar to animal mucus, thoughits nature is obscure. This matter forms about2 per cent, of the serositv, and the remainingsolid contents amount to about 10 per cent,more.

Dr, Marcet 0 has given some valuable ex-periments on the contents of the serosity ascompared with those of other watery fluids ofthe animal body, whether natural or morbid.The specific gravity of serum varies remark-ably, being found from 1021.5 to 1032.5. Ona careful analysis he gives the following as theconstituent parts of serum, the dry contentsbeing all thoroughly desiccated in a sand heatwithout charring or decomposition :

Water. 900.00

Albumen.86.80

Muco-extractive matter . 4.00

Muriat of soda with a lit-7 g gQtie muriat of potash . 5Sub-carbonat of soda . 1.65

Sulphat of potash . . 0.55

Phosphats of lime, iron, 7 q (jq

and magnesia ... 5

1000.00

It will be seen therefore that serum containsa tenth of its weight of solid contents, nine-tenths of which are animal matter, and therest saline.

Dr. M. agrees with Dr. Bostock in assertingthe total absence of true gelatine in serum, butallows a kind of muco-extractive matter, whichis distinguished by being incoagulable, and so-luble in water and other menstrua. The littlealbumen with which it remains combined afterthe serum has bee* heated is entirely separableby being boiled with corrosive sublimate.

Since the publication of Dr. Bostock’s paperMr. W. Brande has made some chemical re-searches -on the blood, d in which he has veryhappily applied the galvanic influence, in orderto detect the real nature of the animal matterthat remains in serosity after the coagulationof the bulk of the albumen by a boiling heat.One ounce of pure serum was diluted withwater, the conductors from a battery of thirtypairs of four inch plates were immersed in thissolution at a distance of two inches from eachother, and the whole of the albumen coagu-lated in contact with the negative ware inthree hours and a half, the coagulum beingoccasionally removed. A similar effect wasproduced in the serosity after the greater part• Medico-Chirurgical Transactions.

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of the albumen had been coagulated by heat;the fluid was then exposed to the galvanicaction, and albumen coagulated at the negativewire. In both cases the fluid, evaporated afterthe galvanic action was over, gave no changeon adding infusion of galls, nor afforded anygelatine when dry. On the other hand, somesolution of isinglass was added to serum, andthe galvanic action applied, but after all coagu-lation had ceased, the liquid still gave a copiousprecipitate by galls. Hence it appears thatgalvanic electricity has no effect in separatinggelatine from its solution, though it totallyprecipitates albumen. It was also found thatheating serum with the addition of a littlemuriatic acid, as effectually coagulates the wholeof the albumen as is done by the agency ofgalvanism.

Mr. Brande has given some additional factsrelative to the properties of the colouring matterof the blood, which (as well as those of pro-fessor Berzelius , to be presently mentioned)throw much uncertainty on the hypothesis ofFourcroy and Vauquelin , that the colour isgiven by a sub-phosphat of iron dissolved inserum, and indeed make it doubtful whetherthis metal is at all concerned in giving toblood its deep and beautiful colour. Thecolouring matter was generally obtained bystirring venous blood with a stick as soon asdrawn; the fibrin collects at the end of thestick, and the colouring matter is diffusedthrough the serum, from which it graduallysubsides, and may therefore be collected in avery condensed form though still mixed withserum. This substance readily dissolves inwater, making a bright red solution when fil-trated, which however becomes brown andseparates by a boiling heat into a clear colour-less water and a brown sediment. Muriaticacid, poured upon the dense colouting matterabove described, renders one portion brown andinsoluble, but dissolves the other portion into aliquid, which when filtrated is a dark crimsonin reflected light,- but greenish in transmittedlight. The colour is not altered by long ex-posure to light, nor by a boiling heat, normaterially by alkalies, nor by galls. The dilutesulphuric acid extracts the colouring matter aswell as the muriatic. Both these solutionsmay also be made by digesting at a heat of150° to 200° some pieces of the commoncoagulum of blood with the acid employed.If muriatic acid, it may be diluted with anequal quantity of water; and if sulphuric,vol. 2. i Phil, Trans, for IS 12. j