Scientists in Britain have applied for a license to create part cow, part human embryos to be used in producing stem cells.

The researchers intend to test a procedure for putting human D.N.A. inside animal eggs - creating a hybrid embryo that is 99.9 percent human, and .1 percent animal. The embryo would be destroyed after 14 days.

The goal is to produce a plentiful supply of stem cells, which are master cells that can turn into any kind of tissue. Scientists hope stem cells can be used in treating diseases such as Parkinson's and Alzheimer's.

If the application is approved by Britain's Human Fertilization and Embryology Authority, scientists say it could help researches overcome current difficulties in obtaining human eggs.

The proposal has been criticized by ethics groups that say it could blur the line between animals and humans.

A decision on the application is expected to take several months.