Medicinal leech

In pre-scientific medicine, the medicinal leech (Hirudo medicinalis) was used to remove blood from a patient as part of a process to "balance" the "humors" that, according to Hippocrates, must be kept in balance in order for the human body to function properly. (The four humors of ancient medical philosophy were blood, phlegm, black bile, and yellow bile.) Any sickness that caused the subject's skin to become red (e.g. fever and inflammation), so the theory went, must have arisen from too much blood in the body. Similarly, any person whose behavior was strident and "sanguine" was thought to be suffering from an excess of blood.

Ironically, modern medicine again has a use for medicinal leeches. They provide an effective means to reduce blood coagulation, relieve pressure from pooling blood, and stimulate circulation in reattachment operations for organs with critical blood flow, such as eye lids, fingers, and ears.

External references

• medicinal leeches (hirudo medicinalis) in modern medicin, for replantativ and plastic surgery
• University of Michigan Animal Diversity Web: Hirudo medicinalis (medicinal leech)
• Model Systems in Neuroethology: Swimming in the Medicinal Leech