They are rhomboidal, of a dirty brown colour, quite characteristic, and require to be seen with a magnifying power of three hundred or four hundred diameters. With the smallest quantity of blood these two reactions can always be produced—the spectrum examination and the crystals of hydrochlorate of hæmatin; and they are so certain that the existence of one alone enables one to affirm the presence of blood.
3. The third process, though not so exact as the preceding, ought, nevertheless, never to be neglected. If to a very small quantity of blood dissolved in a little water be added a few drops of tincture of guaiacum and of binoxide of hydrogen, a persistent blue colour is immediately produced; but this very sensitive reaction can be obtained with other organic matter, such as nasal mucus, saliva, &c.; it therefore only gives a probability. We must proceed in the following manner:—A tincture of guaiacum is prepared with alcohol at 83 degrees, and guaiacum resin; a mixture of sulphuric ether and binoxide of hydrogen is also made, and enclosed in a stoppered bottle, and kept under water in the dark. This preparation is less liable to change than pure oxygenated waters. The object stained with blood, if it be white, is put into a little cup, then moistened with water to dissolve out the blood stain, and washed in distilled water; this water is then submitted to the action of these reagents.
If the thing stained be coloured, and the stain little or not at all visible, it must be moistened, and then pressed between two or three sheets of white blotting-paper, and tried first with the guaiacum. If the stain be of blood a reddish or brown spot will form on the paper.
One of the sheets should be treated with ammonia, and the stain will become crimson or green. A second sheet treated with tincture of guaiacum and ozonised ether will give a blue colour more or less intense, according to the quantity of the blood.
To recapitulate:—1. If the stains or scales of blood appear recent, the corpuscles may, after the necessary precautions, be examined under the microscope, and their presence, diameter, &c. observed, which will enable one to diagnose the origin of the blood, whether human or animal. 2. If the stains be old and the blood changed, the reaction with the tincture of guaiacum would make the presence of blood probable; but its actual presence cannot be affirmed without spectrum examination or the production of crystals of hydrochlorate of hæmatin; one of the two is sufficient. It is unnecessary to add that these reactions do not show whether the blood is human or animal.
Bullocks’ blood has of late years, more especially in France, come into use as a remedy for anæmia and pulmonary phthisis. A correspondent, writing from Paris to the ‘Medical Times and Gazette’ in 1872, says: “It is a curious sight to see the number of patients of both sexes and of all ranks and ages, who flock to the slaughter-house every morning to drink of the still fuming blood of the oxen slaughtered for the table. I was struck with the facility with which young ladies take to it, and I have heard many say that they prefer it to cod-liver oil.”
In a paper read in 1872 before the Academy of Sciences in Paris by M. Boussingault, detailing his researches into the composition of blood, the author expressed his surprise that bullock’s blood was not more generally used as a food, as it contains all the constituents of a
perfect aliment. According to the above chemist, of all nutritive substances the blood of animals contains the largest amount of iron. In man, Boussingault found in 100 grammes of blood 51 milligrammes of iron; in that of the ox, 55 milligrammes; of the pig, 59 milligrammes; and in that of the frog, 42 milligrammes. But it was not only in red blood that iron was found, Boussingault detected it in white blood also; and he found the blood of snails to contain as much iron as that of the ox or calf.
A simple and ingenious method for the therapeutic administration of the serum of the blood of sheep and oxen has been lately devised by Dr Francis Vacher, the medical officer of Birkenhead. Dr Vacher takes the blood of these animals, allows it to stand until it clots, removes the clot, and dries it at a gentle heat in a hot-air chamber. By this means he obtains a nearly odourless and comparatively tasteless powder, which is ten times the strength of fresh serum. To this preparation he gives the name “serum sanguinis exsiccatum.” He believes that his dried serum will prove a valuable nutrient in consumption, scrofula, diabetes, and loss of flesh.
Uses, &c. That of bullocks is employed for the clarification of wines and syrups; also in the preparation of adhesive cements, as the vehicle in coarse paint for outdoor work, as a manure, as a bleaching powder, to make pure animal charcoal, and for several other purposes. The blood of sheep, pigs, and bullocks, mixed with flour or oatmeal, and seasoned, is eaten by the common people, but it is rather indigestible, and apt to induce disease. Gut-skins stuffed with this mixture form “black puddings.”