red colour of the blood indicates to us that it is still present. If we use hydrogen peroxide, then we lose any control over the blood contained in the tissue. If one is not quite certain of the fact that the organ is free from blood, one should squeeze out a few pieces of it in a little water, and examine the fluid with the spectroscope.
About a hundred times more distilled water than there is of the tissue is placed in an enamelled vessel and then brought to the boil. The tissue, having been absolutely freed from blood, is placed in the boiling water, for every litre of which it is advisable to add about five drops of glacial acetic acid. This is boiled for ten minutes, and the boiling water is passed through a sieve; the tissue is thoroughly rinsed for about five minutes with distilled water, and the same process of boiling is repeated, using fresh water without the addition of acetic acid. The boiling, the pouring off of the boiled water, the rinsing of the tissues, and the renewed boiling are repeated about six times without interrtiption. If it is necessary to cease boiling, then one must never forget to pour a fairly large quantity of toluol on the top of the boiled water containing the tissue. If this be omitted the tissue is liable to become infected, and then some hours of boiling may be necessary in order to free the organ again from extractive substances which react with ninhydrin.
