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The actions of both reversible and irreversible anticholinesterase drugs on the nerve-free smooth muscle of the chick amnion are described. The tertiary compound physostigmine and the irreversible inhibitor diisopropylfluorophosphonate were found to be active in causing contractions, whereas the quaternary compound neostigmine and the irreversible inhibitor Mipafox were only slightly active in this respect. Manometric studies showed that all four compounds were highly active, however, in inhibiting the cholinesterase found in the chick amnion. The effects produced by these compounds in the organ bath are thought to be due to the accumulation of endogenously produced acetylcholine within the tissue. Evidence for an intracellular action of endogenously produced acetylcholine in the smooth muscle of the chick amnion is discussed.

The slow contraction of smooth muscle produced by human plasma becomes less potent after storage of the plasma for six months at room temperature and after processing of the plasma with kaolin. These observations fall into line with the fact that 40% of the initial smooth-muscle-contracting activity of the plasma can be accounted for in the deposit which is formed during the six-months period of storage, and also with the fact that the recovery of G acid from human plasma treated with kaolin is about 50% of the yield which is obtained from the same plasma before kaolin treatment.

Substances capable of stimulating smooth muscle are produced on the incubation of bovine colostrum with urinary kallikrein or calf saliva. These substances, called urine- and saliva-colostrokinin, have been differentiated from kallidin, substance A and similar smooth muscle activating agents. Saliva-colostrokinin is likely to be formed in the suckling calf. Further, as colostrum became milk, the ability to form colostrokinin diminished. A function for saliva-colostrokinin in the newborn is suggested.