He didn't have a donor catalogue because unknown to his patients, all of the sperm he used to inseminate his patients came from one donor, Dr. Jacobson himself.

他没有精者名单，因为他瞒，给她们工授精的部精子都来自同一者，雅各布森医生自己。

There is a catch, though: artificial insemination in African elephants with semen that has been frozen, as opposed to the fresh stuff, has not so far been done successfully.

到目前为止，用事先冷冻的精子（而非新鲜精子）为非洲象进 行工授精的尝试都失败了。