Memoirs for the natural history of humane blood, especially the spirit of that liquor by Robert Boyle.

Particulars referable to the Third Part of the History.

Experiment. I.

A Young Man having bled into a Porringer, and the Blood having been kept several hours, that a sufficient separation might be made of the Coagulated or consist∣ent part and the fluid, the fibrous por∣tion and the Serum were separately weighed: and the difference of the two masses in point of weight was not so great as one would have ex∣pected, the curdled part of the Blood weighing about six Ounces, and the Serous part not many drams from that weight. This Tryal is here set down by comparing it with some others, what difference there is be∣tween the Bloods of sound Persons,

as to the proportion of the Serum, and the concreted part.

Experiment. II.

HUmane Urine, having first (that I know of) by the very ingenious Mr. Hook, and often∣times by me, been observ'd, when frozen, to have on the surface of the Ice, figures not ill resembling Combs or Feathers; the great affinity gene∣rally supposed to be betwixt Ʋrine and the Serum of Blood, made me think fit to try at once whether this last nam'd Liquor would freeze with such a degree of Cold, as would easi∣ly, and yet not very easily glaciate water, and whether, in case it should freeze, the Ice would have a surface figur'd like that of frozen Urine. But, having for this purpose exposed some Serum of Humane Blood to the Cold Air, in two freezing nights

consecutively, the Serum was not found to congeal, tho some Grumous parts of the same Blood did, as has formerly been noted, yet I scarce doubted, but an exceeding hard frost would have produc'd, at least a thin Plate of Ice upon the surface of our Liquor. And to confirm this Con∣jecture, we took the same Serum, and having strained it through a Lin∣nen cloath, to separate the Liquor as much as by that way we could, from any clotted or Fibrous Parts, that might have lain conceal'd in it, we put it into a shallow, concave glass, and laid that upon some of our Frigorifick mixture, made of Ice and Salt, which we have described, and often made use of, in the History of Cold. By this means the exposed Serum, being frozen from the bottom upwards, there appeared here and there upon the Ice contiguous to the Air, cer∣tain Figures, that did not ill resem∣ble those of Conglaciated Urine.

Experiment. III.

HAving formerly had occasion to observe that Mans Urine would tolerably well serve for what they call an invisible Ink: and have∣ing consider'd (when I remembred this) the great Affinity that is sup∣pos'd to be between Urine and the Serum of Blood, I thought fit to try, whether the latter might not be em∣ploy'd like the former to make a kind of invisible Ink, To this effect we took some Serum of Humane Blood, and having dipt a new Pen in it, we trac'd some Characters upon a piece of white Paper, and having suffer'd them to dry on, we held the unwritten side of the Paper over the Flame of a Candle, keeping it always stirring, that it might not take fire. By which means the Let∣ters that had been written, appear∣ed

on the upper surface of the Paper, being tho, not of an Inky Blackness, yet of a Colour dark enough to be easily legible and very like to some others that having been purpose∣ly written with fresh Urine, and made visible, by heat, were com∣par'd with them.