______ and compulsory immunization for diphtheria were not introduced until the 1940s.

Which noxious chemical is a powerful vasoconstrictor?

a. Bradykinin b. Serotonin

Which of the following enzymes, which breaks down carbohydrates, is contained in saliva?

A. Trypsin B. Pepsin C. Chyme D. Lactase E. Amylase