Fisherman,
Fetal blood cells persist in the maternal blood because they are nucleated and able to reproduce.
Erythrocytes in adults are simply capsules of hemoglobin and when they become damaged, they are broken down and excreted. The technical term is enzymatic degradation. This happens with both your own blood and donated blood.
As the cells in an organ age, they die and are replaced. The dead cells are broken down and excreted. This happens with both your own organs and donated organs.
None of these processes constitutes ingestion.
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I've heard the argument that, "the Bible does not sanction any medical use of blood or other use of blood except for ritual" before, but the idea that a prohibition on the "use of blood" can be derived from the Bible's silence is soundly contradicted by JW literature itself.
To illustrate, the March 1, 1989 issue of The Watchtower described intraoperative autotransfusion explicitly as an "autologous blood use."
"A final example of autologous blood use involves recovering and reusing blood during surgery. Equipment is used to aspirate blood from the wound, pump it out through a filter (to remove clots or debris) or a centrifuge (to eliminate fluids), and then direct it back into the patient. " (Emphasis mine)
The previous two examples of "autologous blood use" in the captioned article were isovolemic hemodilution and predonation. So here we had three autologous uses of blood, two of which were matters of conscience and one of which was not. Clearly some uses of blood are distinguishable from others.
The August 8, 1993 issue of Awake! explicitly acknowledges that allogenic blood is used in the production of the hepatitis B vaccine:
"These active immunizations include all the baby shots and the injections that are commonly considered as vaccinations. With one exception (discussed later), these do not involve the use of blood in any step of production?..One other active immunization deserves attention because it is the only active immunization made from blood. It is a hepatitis-B vaccine called Heptavax-B." (Emphasis mine)
The October 1, 1994 issue of The Watchtower amplifies on the subject of "baby shots" by acknowledging that blood products are indeed used in their production:
"Many find this noteworthy, since some vaccines that are not prepared from blood may contain a relatively small amount of plasma albumin that was used or added to stabilize the ingredients in the preparation."
Examples would include MMR II, MUMPSVAX, ATTENUVAX and MURAVAX II by Merck & Co. The growth mediums for these vaccines (e.g. Medium 199, MEM, etc) typically contain both human albumin and fetal bovine serum. Additionally the vaccines themselves contain human albumin as either an adjuvant or excipient. (or both) Other examples of this include VARIVAX and VAQTA, also by Merck & Co., EOLARIX, INFANRIX, and GLAXO by SmithKline Beecham, PENTACEL by Aventis Pasteur, and Connaught Laboratories IPV just to name a few. The acceptance of some of these vaccines is virtually unavoidable in modern society.
Invoking an unconditional argument in defense of what they themselves explicitly acknowledge to be a conditional prohibition yet again exposes the confusion of Watchtower writers.