Transfusion of blood is most valuable as _a preliminary to operation_ in patients who are bloodless as a result of hæmorrhage from gastric and duodenal ulcers, and in bleeders. HÆMOPHILIA The term hæmophilia is applied to an inherited disease which renders the patient liable to serious hæmorrhage from even the most trivial injuries; and the subjects of it are popularly known as "bleeders." The cause of the disease and its true nature are as yet unknown. There is no proof of any structural defect in the blood vessels, and beyond the fact that there is a diminution in the number of blood-plates, it has not been demonstrated that there is any alteration in the composition of the blood. The affection is in a marked degree hereditary, all the branches of an affected family being liable to suffer. Its mode of transmission to individuals, moreover, is characteristic: the male members of the stock alone suffer from the affection in its typical form, while the tendency is transmitted through the female line. Thus the daughters of a father who is a bleeder, whilst they do not themselves suffer from the disease, transmit the tendency to their male offspring. The sons, on the other hand, neither suffer themselves nor transmit the disease to their children (Fig. 64). The female members of a hæmophilic stock are often very prolific, and there is usually a predominance of daughters in their families. FIG 64.--Genealogical Tree of a Hæmophilic Family. Great-Great-Grandmother                Great-Great-Grandfather Mrs D. (Lancashire) F                  M (History not known                   .|                  |  as to bleeding)                   .|                  |                   .+----------+-------+                   ............| .|                           ....|                           .+---------+--------+       Great-Grandmother .|         |        |       (Married three .F        MB       MB         times)   .|                     .|                           .|      By First Husband     .|                  By Second           By Third              ..............|                  Husband             Husband   +-----------+------------+----------+-------+-------+-----------+------+   |          .|            |          |       +-------+-----------+------+   M          .F            F          F       |       |           +------+   |          .|            |          |       MB      F Died in      No Died       Grandmother      |          |               | Childbed    Family æt.          .|            |     +-----------+   +----+--- 70          .|        +------+  |had family |   |              .|        |      |  |but history|   |              .|        MB    MB  |not known  | MB              .|              .|              .|............................. +-----+----------+------------+------------+------------+-------------+