﻿1903] CHEMICAL STIMULATION 89 



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KCN is believed to do in animal physiology. Diakonow^^ states 

 that with increasing acidity of the nutrient medium Intramolecular. 

 respiration of molds decreases, but normal respiration Is not 

 sensibly affected. Kosinski^^ finds the respiration of Aspergillus 

 quickened by Zn, Fe, Mn, cocain, strychnin, and not too concen- 

 trated ether ; he tested ZnSO^ as strong as o.i per cent, without 

 its depressing the respiration during the first day. He also 

 reports a stimulation by .0005 per cent. ZnSO^, but this appear- 

 ance is quite possibly due to the growth of his material, as 

 ^ appears more probable from his finding the acceleration not very 



t dependent on the concentration of salt applied. Ono (/. r. 1900, 



p. 156) found that the proper concentration of NiSO^ increased 

 the formation of oxalic acid, but got a similar result with no 

 other poison. The acceleration of fermentation by yeasts, by 

 the presence of traces of poisons, is a very nearly related 

 phenomenon. 



In my measurements of respiration I have used a modification 

 of the Pettenkofer method, which has enabled me to work with 

 an assurance of reliable results not possible with apparatus 

 hitherto used. Respiration varies rapidly with changes in tem- 

 perature, and absolute constancy of temperature is not practi- 

 cable. The best we have been able to do is to make the variations 

 as slight as possible ; and in studying the influence of other 

 factors on respiration, the error from the thermal variations has 

 had to be ignored. Working with water plants this error is 

 augmented by the lesser solubility of CO^ at higher tempera- 

 tures. The rate at which air passes through the apparatus has a 

 more than appreciable influence on the results under any condi- 

 tions; and w^hen working with solutions the solubility of the ^ 

 CO^ makes glaring the results of small irregularities in the rate 

 of flow. When experiments are lasting longer than a few hours 

 the rate of respiration may change, and the possible error from 

 this source is very imperfectly overcome when, with other plants, 



37DIAKONOW, N, W., Intramolekulare Atlimung und Gahrthatigkeit der Schim- 

 melpilze, Ber. Deutsch. Bot. Gesells. 4:2-7. 1886. 



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3^.KosiNSKl, I., Die Athmung bei Hungerzustanden und unter Einwirkung von 

 mechanischen und chemischen Reizmitteln bei Aspergillus nw^r Jahrb. Wiss. 

 Bot. 37:137-204. 1901. 



