另一半

The Canadian researchers randomly assigned about half of the addicts to receive methadone and the other half to receive daily injections of diacetylmorphine, the active ingredient in heroin.

加拿大的研究者对【将】受验者随机分组，一半接受美沙酮的治疗，另一半每天接受注射二乙酰吗啡，主成分是海洛因【为海洛因的主成分】。