These experiments suggest the following conclusions concerning hemolytic action:
1. It is probably the proteid part of the serum which inhibits the bile salts.
2. The cholalic acid group is the active part of the bile salt molecule.
3. The protection afforded by bile salts against serum is of especial interest from the following considerations: (a) The protective action is a property apparently peculiar to proteids obtained from blood serum. It is not given satisfactorily by egg albumen. (b) The conjugation of cholalic acid with glycocoll in the formation of the bile salts is of some advantage to the organism. Although the toxicity of the cholalate for red corpuscles, when free from serum, is at most only slightly diminished by conjugation, yet the blood serum possesses a greater inhibiting action for the resulting glycocholate than for the original cholalate.
4. As compared with its inhibition of sodium glycocholate, normal serum possesses relatively little inhibiting action against certain foreign hemolytic agents, such as tetanus toxin, sodium benzoate, phenol and ethyl alcohol.
5. Hemolytic experiments afford a fairly general method for studying, in vitro, certain syntheses occurring in the body. They avoid, largely, the complications, such as rapid chemical alteration, which might occur in animal experimentation.
Contrary to the results obtained with bile salts, the conjugation of benzoic acid and of phenol results in an effective reduction of their hemolytic action independently of the presence or absence of serum.