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.

• Aeither cells secreted hormones, which made them  
• Beither cells secreted hormones, making them  
• Ceither cells secreted hormones and were  
• Dcells either secreted hormones, in which case they were  
• Ecells either secreted hormones, which made them