Germanium

It can be done if absolutely necessary, but usually the circuit will not function properly unless totally redesigned to compensate for the differences between the components. This is rarely worth the trouble unless a germanium substitute is not available and the circuit MUST be repaired at any cost.

So unless you know exactly what you are doing and how to design transistor circuitry from scratch (after reverse engineering the old circuit), consider such substitutions to be impossible.

Available scientific evidence does not support claims that germanium supplements are effective in preventing or treating cancer in humans, and there are numerous reports showing that they may be harmful. A study conducted by the U.S. Food and Drug Administration (FDA) reported that supplements containing germanium present a potential hazard to humans. As a result, the FDA issued an "Import Alert," which allows germanium imports to be seized if they are to be used as a food supplement. However, the amount and type of germanium naturally found in foods do not appear to be toxic.

Available scientific evidence does not support claims that germanium supplements promote health or increase the body's production of interferon. It also does not support the claim that germanium is an essential nutrient in animals or humans.

A study conducted by the FDA found at least 31 cases of kidney failure linked to germanium products. A number of deaths have also been reported. Most of these effects were from inorganic forms of germanium, but the FDA has also found severe kidney damage in people taking germanium that was sold as organic.

Because of the way it is processed, organic germanium is easily contaminated with inorganic germanium, which appears to be more toxic than the organic form. It is uncertain whether the kidney damage and other toxic effects reported in people who took organic germanium were actually caused by the supplement's contamination with inorganic germanium. Because of this problem with purity, supplements containing germanium of any sort might pose a hazard to humans.

In the early 1980s, small studies were done using germanium on people with various types of cancer. In the first study, even those who received the lowest doses had toxic effects, and none of the patients got better. Later, a group of 25 patients were given spirogermanium (an organic germanium product) 3 times a week for 2 weeks. Most patients got worse, and toxic side effects were common. Because of these results-many toxic effects and little effect on the cancer-studies on spirogermanium were stopped.

In 2005, researchers in Arizona started a study to find out if taking pure organic germanium (bis-carboxyethylgermanium sequioxide) might help with radiation-related fatigue. The patients, who have early stage prostate cancer or breast cancer, will be watched carefully for side effects and abnormal laboratory values. The study is still going on, and is expected to finish at the end of 2012.

Germanium supplements may pose danger for humans. Several deaths have been reported in the medical literature, with serious illness in some who survived. While organic germanium appears to be less toxic than inorganic germanium, it has been reported to cause kidney damage, liver changes, and heart problems. Other reported effects include anemia, poor appetite, weight loss, nausea, vomiting, tiredness, muscle weakness, skin rashes, and numbness in the hands and feet due to nerve damage. The toxic effects build up over time and get worse the longer it is taken. Many of these effects improve after the supplement is stopped, but kidney and nerve damage persisted and became chronic for some people.

Germanium may interfere with certain other medicines and may make seizures worse. Drugs for which side effects include kidney problems may be more likely to cause harm if taken with germanium. Very little testing during pregnancy has been reported, but at least one form of germanium caused ill effects on fetuses in animal tests. Women who are pregnant or breast-feeding should not take germanium. At this time, germanium is not recommended as a dietary supplement for anyone due to the potential for serious health hazards.

Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

From wikipedia:

Germanium was discovered comparatively late because very few minerals contain it in high concentration.

Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust.

In 1869, Dmitri Mendeleev predicted its existence and some of its properties based on its position on his periodic table and called the element eka-silicon.

Nearly two decades later, on February 6, 1886, Clemens Winkler found it in the mineral argyrodite, a new mineral from the Himmelsfürst mine near Freiberg (Germany).

Winkler found that his experimental observations agreed with Mendeleev's predictions and named the element after his country, Germany.