题目选项分析

Until Berta and Ernst Scharrer established the concept of neurosecretion in 1928, scientists believed that either cells secreted hormones, which made them endocrine cells and thus part of the endocrine system, or conducted electrical impulses, in which case they were nerve cells and thus part of the nervous system.

Until Berta and Ernst Scharrer established the concept of neurosecretion in 1928, scientists believed that cells either secreted hormones, in which case they were endocrine cells and thus part of the endocrine system, or conducted electrical impulses, in which case they were nerve cells and thus part of the nervous system.