HORMONE SUBSTANCES 113 



mechanism. The stimulant effect of ACh on ciliary activity of 

 the frog pharynx has been confirmed by Kordik, Biilbring 

 and Burn (1952), who found that lower concentrations (10~^ 

 g/ml) of both ACh and eserine (an anticholinesterase) increased 

 the rate of particle transport by the cilia, while higher 

 concentrations of both depressed the activity. Similar results 

 were obtained with ciliated epithelium from the rabbit trachea 

 by these authors, and in both tissues atropine slowed the activity. 

 There is no certainty in these cases that ACh does not act on 

 nerve tissues which could influence the ciliary activity. 



In an attempt to use a ciliated tissue free from nerve and muscle, 

 Biilbring, Burn and Shelley (1953) experimented on the frontal 

 cilia of Mytilus gill filaments. It is unfortunate that these gill 

 filaments have been shown to contain both muscle and gland cells 

 (Lucas, 1931a). In their experiments Biilbring, Burn and Shelley 

 found an increase in both the rate of particle transport (11 per 

 cent at 10~^ g/ml) and the rate of beat (10 per cent at 10~'^ g/ml) 

 with ACh bromide, while both activities were slowed at higher 

 concentrations. Similarly, eserine sulphate increased the rate of 

 particle transport over a wide range of concentrations, and only 

 at a very high concentration (5 x 10~^ g/ml and above) did it 

 depress this activity; this substance had little effect on the rate of 

 beat except for some slowing at the higher concentrations. Atropine 

 gave much the same results as ACh, instead of the opposite effect 

 that one would expect, but ^-tubocurarine reduced ciliary activity 

 at all concentrations, as it should do if it antagonizes ACh. The 

 effect of ACh on particle transport seems to be mainly the result 

 of changes in the rate of beat, for Aiello (1960) found that while 

 both eserine and a mixture of eserine and ACh slowed the 

 frequency, they did not affect the metachronal wave velocity. 



Biilbring, Burn and Shelley have been able to show the presence 

 of ACh in normal gill filaments by both pharmacological assay 

 and paper chromatography, and a chdlinesterase enzyme, which is 

 necessary for the breakdown of ACh, was also present. These 

 authors had some difficulty in finding a choline acetylase system 

 for the synthesis of ACh, but its presence in the gill filaments of 

 Mytilus has been confirmed by Milton (1959). It would be most 

 interesting if it could be proved that the ACh is associated with 

 the ciliated cells rather than the muscle or gland cells, and that 



