(c) Another method may be adopted. First determine the side of the cloth on which the stain is present, and cut out the stain, leaving a small strip of cloth attached to the main portion. Place the end of the strip in a little water in a watch-glass, so that the water by capillary attraction may permeate the entire stain. With a thin-bladed knife gently remove the moistened stain and place it on a microscopic slide, and examine as before.
Fixing and Staining.—A drop of the watery extract of the stain may be placed on a microscope slide and allowed to dry in the air, covered to protect it from dust, and then fixed by heating the slide over a spirit or Bunsen flame or by the use of absolute alcohol. When fixed, the preparation can be stained with eosin and methylene blue, methylene violet, or other nuclear dye. The film may also be fixed and stained with Leishman‘s solution in one procedure, or fixed by heat first and then stained with Leishman. The procedure is the same as for blood, viz. to cover the film with a few drops of Leishman‘s stain, let stand for two or three minutes, then add a few drops of distilled water, in two or three minutes wash in distilled water, dry with filter paper, and examine with the oil immersion. The preparation may be mounted in Canada balsam and preserved for further reference. The head of the spermatazoon takes the nuclear dyes in ordinary use. The spermatazoa are best found in the centre of the stain. If the stain be small the watery extract may be centrifuged.
Florence‘s Reaction.—A useful chemical reaction has been introduced by Dr. Florence of Lyons. It depends upon the reaction between a concentrated solution of iodine in potassium iodide and human semen. A watery extract of the stain is made, and a drop placed on a microscope slide, by
| Potassium iodide | 1.65 | grms. |
| Iodine | 2.54 | “ |
| Distilled water | 30 | c.c. |
The drops are covered with a cover glass and examined; where the two drops unite, a precipitate is formed which consists of brown crystals, very similar to hæmin crystals. If there be sufficient material the precipitate may be obtained in a test tube. This test is extremely delicate, and is analogous in value to the guaiacum reaction for blood. A positive reaction does not absolutely prove that the stain is seminal, but a negative reaction proves that it is not. Dr. Florence holds the reaction is specific for human semen, as he has failed to obtain it with the seminal fluid of any other animal, or other fluids or tissues. He considers it due to the presence of an alkaloidal body in human semen, which he calls virispermin.
The crystals are said by Dr. Max Richter to form on the addition of the iodine solution to decomposition products of lecithin.
The author has found this reaction extremely delicate, even with minute traces. The crystals form rapidly and are easily recognisable. They, however, are evanescent and disappear on standing, so that they cannot be preserved as microscopic specimens.
The biological test.—This is carried out in the same way as the biological test for blood. Dr. C. G. Farnum, who proposed this test, uses semen or testicular emulsion for antigen, injecting 5 to 10 c.c. into the peritoneal cavity of a rabbit at intervals of from two to six days, on five or eight occasions. The antiserum is diluted from twelve to eighteen times with normal saline, and the semen four to twenty-five times. Human antiserum gives a precipitin reaction with the watery extract of human seminal stain, but not with testicular emulsions of the bull, dog, or goat, or with human blood serum.[14]
Can a Rape be committed by one man on a healthy, vigorous woman?—The answer to the question will, to a great extent, depend on the relative strength of the conflicting parties. Every case of rape has to be judged on its own merits. In any case, the medical jurist has simply to state, from the examination of the parties, that sexual intercourse has taken place, leaving the jury to decide whether a rape or not has been perpetrated. A case is mentioned by Casper where a healthy, strong adult of twenty-five years old was violated by a single man.
Can a Woman be Violated during Sleep?—By this is intended natural healthy sleep, and not that induced by narcotics. In natural sleep, rape is scarcely possible in a virgin, especially if the hymen be found recently ruptured, though it may be possible in a woman accustomed to sexual intercourse.