BLOOD STAINS 101 the poorly marked reaction with group A serum or group B serum must be read as positive. It should be noted that dried serum retains its agglutinating property, and even though drying destroys the red Hood corpuscles it does not destroy their agglutinogens. Moreover, the group specific substances, viz. the ag- glutinogens (isogens) A and B are not confined only to the red blood cells, but are to be found also in the cells of almost all the tissues, organs and body fluids or secretions, such as saliva, nasal secretion, gastric juice, urine, vaginal secretion, semen, milk, bile, sweat, etc. ; they are not found in nerve tissue ; epithelium, skin appendages, bone, cartilage and cerebro-spinal fluid. The agglutinins a and b, on the other hand, besides being present in the serum, are also present in body fluids rich in serum proteins, e.g. milk, lymph, exudates, transudates, etc. Strictly speaking, the groups are not of the blood but of the whole tissue structure of the body. Thus, the group of a dead body may be determined by means of the serum agglutinins as long as any serum is available, and after that by means of the tissue ag- glutinogens. These persist and remain identifiable until putrefaction is far advanced. All individuals can be divided into two types, viz. secretors and non- secretors in accordance with the presence or absence of group specific sub- stances in their body fluids or secretions. In individuals, who are called secretors, these substances are present in high concentration in their secre- tions, such as saliva, gastric juice, semen, etc. In individuals, who are known as non-seeretors, these substances are absent from then? body fluids. The ability to secrete these substances in body fluids is inherited as a mendehan dominant, and remains constant throughout life. The medico-legal application of this test lies in the determination of cases of disputed paternity and in the grouping of blood stains in criminal cases. Cases of Disputed Paternity.—In 1910, Von Dungern and Hirschfeld showed from experiments that the agglutinogens A and B are Mendelian dominants, and are transmitted from parent to offspring according to the well-established laws of inheritance. Bernstein has demonstrated that O is recessive to both. Weiner31 has drawn up the following table showing the possible and impossible children occurring in various blood groups of parents: — Blood Groups of Parents. Possible blood groups of Children. Impossible blood groups of Children. o:x o 0 A, B, AB O.X A 0, A B, AB 0 X B 0, B A, AB A X A O, A B, AB A X B O, A, B, AB 3Tone B X B 0, B A, AB 0 X AB A, B O, AB A X AB A, B, AB 0 B X AB A, B, AB 0 AB X AB A, B, AB O Many thousands of families have been examined by the above described formula and no real exceptions have been discovered. It is obvious from the above-mentioned table that a specific agglutinogen cannot appear in a child unless it was present in at least one of its parents. For instance, if the iso-hsemagglutinogen (isogen) A is present in a child, but not in its 31. Amer. Jour. Med. Sc,, Aug. 1933, CLXXXVI, p. 257.