Volume 25, Issue 6
June 1947, pages 163-194
pp 163-172 June 1947
The nature of response of frog’s stomach muscle to nervous stimulation is described. The contraction is similar to that produced by acetylcholine and potassium, and is not of the same type as that produced by alternating current, suggesting that acetylcholine is liberated during nervous stimulation of frog’s stomach. Excitation by nervous stimulation appears to involve the potassium ion.
Nervous stimulation also produces a contraction similar to that produced by alternating current, thus suggesting that electrical transmission precedes chemical. It is suggested that chemical transmission imparts tome properties to the effects of electrical transmission.
On nervous stimulation, circular fibres of the stomach give the second kind of contraction, and longitudinal the first kind or tonic contraction. It is probable that the function of the longitudinal fibres is to maintain a tonic pressure on its contents and prevent the sagging of the stomach, and that of the circular fibres is to mix the contents by rhythmic contractions, as well as to exert a tonic pressure.
pp 173-177 June 1947
In the presence of growing roots of wheat, radish, rice andjowar in Ashby’s cultures,Azotobacter fixed larger amounts of atmospheric nitrogen than in their absence. The stimulating effect, however, varied with the kind of plant used, wheat exerting the greatest beneficial effect followed closely by radish. Rice andjowar were poor in this respect and exerted an almost equal degree of stimulation.
None of the seeds tested possessed any power of fixing elemental nitrogen during germination and the subsequent growth of the seedlings.
pp 178-187 June 1947
pp 188-194 June 1947