THE PROCESS OF NUTRITION. 469 



From the preceding paragraphs it will be evident that the old analogy 

 between the absorption of food and the processes of assimilation, respira- 

 tion, secretion, and excretion in animals and plants, will not hold good. 

 We are not indeed able at present to supply its place according to the 

 requirements of organology from a more simple and correct point of 

 view, for we have but single facts to deal with, and they are too few in 

 number to enable us to unite them into a system free from objections. 

 It is easy enough to see the fallacy of the analogy hitherto supposed to 

 exist between certain processes in the animal and vegetable organisms ; 

 but it is most difficult, and at present impossible, to substitute a new 

 arrangement of facts, because here, as everywhere else, we are sur- 

 rounded with a vast mass of useless investigations, and are almost 

 totally unprovided with serviceable materials on which to found a basis 

 for our theory. Men have contented themselves by drawing out ro- 

 mances and theories, the mere offspring of fancy, supported only by the 

 slightest and most superficial phenomena ; and even in our own century 

 there is carelessness and crudeness about our physical and chemical 

 investigations which savours very much of the ignorance of the middle 

 ages. The most senseless experiments have been made in perfect igno- 

 rance of physical, chemical, and physiological facts, and on the supposed 

 results obtained from them false theories have been put forth. Expe- 

 riments in which plants have been placed in pulverised marble with 

 water saturated with carbonic acid, and from which has been deduced the 

 supposed fact that carbonic acid is unfit for the nourishment of plants, 

 are as senseless as if a zoologist should feed an animal with strychnia, 

 and should thence make the deduction that food containing nitrogenous 

 matters is not wholesome. 



Experiments upon the phenomena of life in plants can only be of 

 value when performed in one of two different ways: either the plants on 

 which they are made must be allowed to vegetate under all their natural 

 circumstances, means being taken which shall enable us to observe the 

 processes going on in them according to time, measure, and weight ; or 

 else we must compare the phenomena of vegetation according to time, 

 measure, and weight in a plant excluded from one or more natural con- 

 ditions, with the same phenomena in a plant placed under natural cir- 

 cumstances. Both kinds of experiments should have only one end in 

 view, the understanding of the phenomena of life ; and yet we shall not 

 succeed unless we subject the elementary matters and powers which 

 exercise an influence on the plant independent of itself, to an accurate 

 investigation, and understand thoroughly the peculiarity of their action. 

 Since the time of De Saussure innumerable experiments have been 

 performed to ascertain the capacity of plants to select their own nourish- 

 ment ; and the theories and consequent contentions upon the subject 

 would fill a small library. It appears to me, at least since the dis- 

 covery of Dutrochet, that all disputes upon this subject are useless, 

 until we have ascertained whether the organic or the inorganic matter 

 present in the plant may not, independently of the life of the plant, 

 exercise a power of affinity, and how far this harmonises with the 

 phenomena already observed in the plant. 



The question must be thus placed : how do albumen, gums, and sugar 

 behave in the endosmotic apparatus towards a number of soluble salts ; 

 and how would they behave if many of these salts should be mixed with 

 them ? The salts used in this case should be such as are commonly 

 diffused in water and on the earth. If we, therefore, allow plants, in 



H H 3 



