110 -V '. '••• \\ * Fig. 27.—Microphotograph o£ Human Spermatozoa X 900. (Ret Bahadur K. N. Bagchi) or their ova which infest the female genitals. A medical jurist is rarely re- quired to examine a fresh specimen of semen, although he may be called upon to find out living spermatozoa in the vagina, if a female is brought to him soon after an alleged rape. A drop of mucus is removed from the vagina by means of a glass rod, is placed directly on a slide, and is diluted with a drop of normal saline. It is then covered with a cover glass and examined under the high power of a microscope, when motile spermatozoa, if present, will be seen. Dried seminal stains cannot be examined so easily. They re- quire suitable solvents for bringing out spermatozoa under the microscope. A solution containing one drop of hydrochloric acid in 44 cc. of water is considered the most suitable for obtaining the suspensions of spermatozoa from dried stains on fabrics. A ten per cent solution of glycerin in water or in normal saline has been suggested as a useful solvent, but it is regarded as unsuitable for making dry specimens on slides for staining. To suit the climatic conditions of Upper India, Dr. Hankin,50 late Chemical Examiner to the Governments of the United and the Central Provinces, elaborated a me- thod for detecting spermatozoa in seminal stains. The method, consists in boiling the stained fabric in a tannin solution before dissolving it in a solu- tion of potassium cyanide so as to render the spermatozoa capable of removal. The fabric is then placed on a slide, teased with dissecting needles and stained with carbol fuchsia, when it is examined with a medium power lens. This method is too long and complicated to be of any use in a laboratory where a large number of seminal stains are examined every day. A simpler method, which is equally effective and is largely used, consists in moistening a small strip of the stained fabric with a few drops of acidu- lated water in a watch glass for thirty to sixty minutes in the case of fresh stains and for three to four hours in the case of old stains, and keeping it covered to prevent drying. During this period the spermatozoa are softened 50. Brit. Med. Jour., 1906, Vol. II, p. 1261.