HAIR 113 four days. In 1928, Hektoen and Rukstinat 5S showed that an antlserum produced by immunizing rabbits with human semen is both species specific and semen specific, that is, it gives a positive reaction with human blood and also with human semen. In order to demonstrate the semen specific property of the antiserum its species specific property is at first exhausted completely by precipitation with human blood serum, and then the residual or semen specific property is tested with human semen. This test has evidently a bright future, and is likely to be of much practical value in those cases where it has to be determined whether a semi- nal stain is of human origin or derived from an animal. It must, however, be remembered that the bacterial action which produces disintegration of sper- matozoa in seminal stains in the tropics is equally effective in decomposing or digesting the protein constituents of semen which, acting as the antigen, produce antibodies. Such seminal stains with their completely disintegrated protein constituents cannot possibly give a positive precipitin reaction and, therefore, offer the greatest difficulty in giving a definite opinion. The group specific agglutinogens, when present, occur in a highly con- centrated form in the seminal fluid, and it may be possible to ascertain the group of the individual by performing the test for detecting the presence of these agglutinogens in the seminal stains in. the same manner as with blood stains. HAIR The detection of hairs upon weapons, blood stains, or upon the clothing or person of an assailant or a victim forms not unfrequently a very important chain in the evidence of cases of alleged assault, murder, rape, and un- natural offence. The examination of hairs also becomes very necessary in identification, particularly when unknown bodies or fragmentary remains have been sent for medical inspection. While examining hairs the following points have to be determined: — 1. The nature of hairs. 2. The source of hairs. 3. The character of hairs showing the manner of extraction. 1. The Nature of Hairs.—Human hairs have to be distinguished from these of lower animals as also from fibres derived from clothing. For this purpose hairs should be washed hi water, alcohol, ether and oil of cloves successively, and mounted in Canada balsam, and then should be examined under a microscope. A human hair consists of a root and a shaft. The root is lodged in the hair follicle which is implanted in the skin. The shaft is that portion of the hair which projects from the surface of the skin. It is entirely epithelial and^ consists, from without inwards,," jSfjEheT, cuticle,^ cortex ™arid" irieHuHaJ "The cuEcIeT is composed ofsT thin layer of "very fine Mbricate^sceiles- which overlap one another from below upwards. The cortex""consists of elongated cells which are closely joined together to form flattened fusiform fibres. These fibre^contein^iigmenL granules in dark^hai^and^ hair. The medulla is lacking in many fine hairs ancfj when present in the thicker hairs, it consists of pol^^e^al^cefls-arran^ed-jin^dojible .rows.._Minute air- buBbfes^a^e^ires^nf^between, and sometimes within, the cells of both the medulla and cortex, and cause the hair to look white by reflected light. Distinction between human and lower animal Hairs.—To distinguish between the hairs of human beings and those of lower animals the micros- copic features represented by the cuticle, medulla and cortex should be observed. 58. Arch. Path., 1928, 6, p. 96.