278 



PHYSIOLOGY OF NUTRITION. 



in germination, and those afforded by analytic investigations, we 

 are justified in the conclusion that the whole of the Carbon leaves 

 the germinating seeds in combination with Oxygen as Carbon 

 dioxide. For details as to the method of procedure the treatises 

 cited in the footnote must be consulted. Respecting the ultimate 

 analyses, to secure success in which much practice is essential, 

 I will only observe further that the seed and seedling substance, 

 in consideration of the Chlorine and Sulphur contained in it, must 

 be mixed before the combustion with Lead chromate, and that in 

 consideration of the Nitrogen contained in it, metallic Copper 

 (copper turnings) must be placed at the front end of the tube. 

 The combustion itself is best performed in a stream of Oxygen. 1 



1 See Sachsse, Ucber einige chemische Vorgilnge bei der Keimung von Pisum 

 sativum, Leipzig, 1872 ; Detmer, Physioloyisclie UntersucTiungen ilber die Kei- 

 olhaltiger Samen, etc., Jena, 1875. 



106. Absorption of Oxygen in Respiration, and Determination 



C0 21 

 ' 



of the Respiratory Ratio 



For researches whose object is to determine the quantity of 

 Oxygen absorbed, and at the same time the quantity of Carbon 



dioxide produced, in normal respira- 

 tion, the apparatus represented in 

 Fig. 103 may be employed. 



The bell-glass, a, about 800 c.c. 

 in capacity, and provided with a 

 carefully ground broad rim, rests 

 on a ground glass plate. The rim 

 of the bell-glass is well greased 

 with a mixture prepared by melting 

 together 1 part of wax and 3 parts 

 of lard. The tubulus of the bell- 

 glass is fitted air-tight with a 

 rubber stopper, which receives the 

 tubes r 1 and r. The tube r is pro- 

 vided with a stop-cock, and serves 



Fm.103. Apparatus, after Stich, for ..* 



determining the amount of Oxygen to put the interior of the bell-glass 



absorbed and of Carbon dioxide pro- in communication with the atmo- 



duced in the respiration of plants. . 



sphere. The long limb ot the tube 

 r, which has an internal diameter of 7 mm., and is graduated to 



