Physiologie der Zellen, Gewebe und Organe. 173 



is not the same throughout the day, but undergoes cliaracteristic variations at 

 different times of day. In one case, in spring, a plant reached its maximum ex- 

 citabilitv, as measured by its response, at Ip.m. There was then a continuous fall 

 until the minimum was reached at 9 the following mox'ning, when the plant was 

 practically insensitive. The excitability than increased in a staircase manner until 

 it again reached the maximum at 1 p. m. 



Externa! changes also modified excitability. Thus sudden darkness caused a 

 transient depression followed by revival of excitability. Esposure to light after 

 darkness produced a similar effect. Excessive turgor diminished the response, and 

 lowering of temperature caused depression culminating in abolition of response. 

 Rising temperature enhanced the excitability up to an optimum, beyond which 

 depression was induced. "The periodic Variation of light, temperature, and turgor, 

 as well as the phenomenon of lag, are factors which determine the periodic Va- 

 riation of excitability observed in the plant." Gates. 



464) Tlioday, D., On the effect of Chloroform on the respiratory ex- 

 changes of leaves. In: Annais of Botany, Bd. 27, S. 697—717, 1913. 



Experiments were made with leaves of Cherry Laurel and other plants 

 under the influence of Chloroform, to determine how this affected the relation 

 between the amount of oxygen absorbed and the amount of COj evolved. The 

 method adopted was to analyze samples of air in a closed Chamber which con- 

 tained the leaves. The analyses were made with the capillary eudiometric appa- 

 ratus of Bonnier and Mangin. 



It was found that in Laurel and Helianthus, the final disorganization of the 

 leaves is accompanied by a large absorption of oxygen. This took place when 

 the leaves turned dark, and is believed to be due to the oxidation of tanuin-like 

 substances by the oxidases after the Chloroform has killed the cells. In Tropae- 

 oluni there is no such discoloration and no such absorption of oxygen. 



During the temporary augmentation of the respiration, which foUows treat- 

 ment of the leaves with smaller quantities of Chloroform, the absorption of 

 oxygen and production of COg appear to remain co-ordinated, botli showing an 

 increase. In leaves which had previously been starved, the Stimulation was usually 

 prolonged. Gates. 



465) Bayliss, W. M., IJesearches on the uature of enzyme action. III. The 

 syntlietic action of enzymes. In: Journ. of Physiol., Bd. XLVI, S. 236, 1913; 



Reactions in the system, glycerol, glucose, glycerol-glucoside and water, as acce- 

 lerated by emulsin, follow in all respects the laws deduced for an equilibrium in a re- 

 versible System, catalyzed by a singie enzyme. Various cases of alleged enzymes pos- 

 sessed of synthetic power alone are shown to rest on faulty evidence. Miues. 



466) Campbell, J. M. H., Douglas, C. G., Haldaue, J. S. and Hobsoii, J. G., The 



response of the respiratory centre to carbonic acid, oxygen, and hydro- 

 gen ion concentration. In: Journ. of Physiol., Bd. XLVI, S. 301, 1913. 



A rise of 1.6 mm in pressure of CO, in the alveolar air increases the luug Venti- 

 lation in man by 100 7o- The tension ofO» may be varied within wide limits without 

 altering this relation. The respiratory centre is exceedingly sensitive to changes in by- 

 drogen ion concentration of the blood. Min es. 



467) Dale, H. H., On the action of Ergotoxine; with special reference to the 

 existence of sympathetic vasodilators. In: Journ. of Physiol., Bd. XLVI, Heft3, 

 S. 291. 1913. 



Experiments on the effect of ergotoxine in modifying the action of adrenine appear 

 to indicate the existence in the cat and dog, but not in the rabbit, of mixed motor-inhi- 

 bitor sympathetic Innervation of arteries in general. Mmes. 



