204 LECTURE XL 



hydrate that the volumes of oxygen absorbed and of carbon 

 dioxide exhaled by it are found to be equal. It has been 

 suggested that this equivalence of volume is due to the oxi- 

 dation of carbohydrate to carbon dioxide and water, accord- 

 ing to the equation, 



C 6 H 12 O 6 + 6 O 2 =6 CO 2 + 6 H 2 O, 



for it has been found that the loss of weight which a starchy 

 seed, for example, undergoes during germination can be 

 accounted for by the disappearance of starch. 



Thus Sachsse made the following determinations with peas : 



Dry weight of peas at commencement 100 grammes. 

 after 184 hours' germination 92*54 



Loss 7-46 



The peas contained Before germination. After germination. 



Fat 2-27 2-03 



Dextrin 6*50 5*41 



Cellulose 7-13 8'io 



Starch 42*44 3343 



Undetermined substances 1376 15 74 



Proteids 23-82 2371 



Ash 4-08 4-08 



loo'oo 92*50 



If, in the case before us, we deduct from the amount of 

 starch lost (9 grammes) by the germinating seeds the amount 

 of starch which is represented by the gain in cellulose and in 

 the undetermined substances (say 2 grammes), we arrive 

 approximately at the total loss of weight (7*46 grammes). 



Though this appears to be a plausible explanation of the 

 loss of weight in these cases, yet it is extremely doubtful if 

 such complete oxidation as that assumed by this mode of 

 reasoning ever occurs in a plant. We should expect to find 

 that respiration would be most active in organs rich in non- 

 nitrogenous organic substances ; but this is not the case. 

 Garreau has found, on the contrary, that respiration is most 

 active in organs which are rich in proteids. The following is 

 a view which is more in accordance with our general know- 

 ledge of the nature of the metabolic processes. We have 



