18 THE PRINCIPLES OF 



which make up the subject of agriculture as it ought, I think, 

 to present itself to the mind of an agricultural teacher. 



But I have also warned my readers against a mistake which 

 is only too common, and shapes itself to me somewhat as 

 follows that there is a strong disposition on the part of 

 those who teach agriculture, or who come before us as 

 agricultural professors, to treat this large subject in a narrow 

 manner. I would describe that treatment as molecular and 

 microscopic, rather than as bold and comprehensive. We 

 have agriculture presented to us as a molecular and micro- 

 scopic subject. When they treat of the soil they enter at 

 once into the constituents of plant food, the action of 

 lacteria in the processes of nitrification, the formation of 

 double silicates, the change from what they call " dormant " 

 to " active " constituents. When they mount a step higher, 

 and treat of vegetation, they fix their attention upon diastasis 

 and the changes which take place in the germination of seed, 

 or in the growing plants, upon the action of chlorophyll, or 

 the peculiar functions of stomata in leaves. Or, when they 

 ascend still higher into the domain of animal life, they dis- 

 course upon the relative size of the liver or of the lungs in 

 pedigree stock as compared with unpedigree stock, the func- 

 tions of saliva and other juices in digestion, or the sources of 

 heat, of fat, or of muscle, the albuminoid ratio, or the digestion 

 co-efficient. 



However worthy of attention and however interesting these 

 topics are, it must be patent to any one that the agricultural 

 teacher who deals with the minute composition of the soil is 

 really teaching agricultural chemistry, not agriculture. Those 

 who go into the minute changes which take place in germin- 

 ation, or in the absorption of gases by leaves, by stem, and 

 by flower, are invading upon the" domain of vegetable 

 physiology, and those who bestow more than a passing 

 attention upon the secretions and functions of the body are 



