Final answer:
The reference information does not specify which country pioneered the use of glycerol in freezing semen samples. Glycerol is used as a cryoprotective agent to protect spermatozoa at an optimal temperature during the freezing process.
Step-by-step explanation:
The country responsible for using glycerol as a way to allow for the freezing of semen samples is not provided in the provided reference information. Glycerol is widely recognized as a cryoprotective agent that is added to semen samples to protect the spermatozoa during the freezing process. To avoid spermatozoa damage, glycerol is mixed with semen at 5°C. By cooling both, the semen and the glycerolated diluent, to the optimal temperature, and then combining them in stages, the integrity of the sperm is preserved during the freezing and subsequent storage phases.