EXPERIMENTS ON ANIMALS 241 



members of the Papilionaceous family. At the same time, it will 

 be granted that further confirmation is essential before such 

 a conclusion can be accepted as fully established." 



This comment reveals the essential conservatism of Gilbert's 

 mind, but the true greatness of the man is seen when we 

 find him, at the age of seventy, repeating the experiments of 

 Hellriegel and Wilfarth, and himself supplying the confirmation 

 of their results which he considered essential. 



The results of these experiments, contributed to the Royal 

 Society in 1887, 1889, and 1890, fully confirmed the theory that 

 leguminous plants are able to assimilate the free nitrogen of the 

 air by means of the micro-organisms contained in their root 

 nodules, and also explained the failure in the 1857-60 experi- 

 ments to demonstrate nitrogen fixation by leguminous plants 

 owing to the use of calcined soil by which the inoculating 

 organisms present in the soil were destroyed. 



Gilbert's investigations from 1871-75 showing that the 

 drainage waters from the experimental fields of Rothamsted 

 contained more nitrates as the amount of ammonium salts 

 applied to the soil increased, have been quoted by some writers 

 as being the basis of the modern theory of nitrification. It must 

 be remembered that Gilbert was at first actively hostile to the 

 bacterial theory of nitrification, and the credit and honour of the 

 work done at Rothamsted on the nitrifying organisms belongs 

 entirely to Warington. 



A few words must suffice for an account of the series of 

 Rothamsted experiments on animals. Series II deals with 

 "Reports of experiments on the feeding of animals, sewage 

 utilisation, &c. Published 1841 1895 inclusive," and contains 

 31 papers. Among the points investigated maybe mentioned 

 the composition of foods in relation to respiration and the 

 feeding of animals; experiments on the feeding of sheep and 

 the fattening of oxen ; some points in connection with animal 

 nutrition ; the feeding of animals for the production of meat, 

 milk and manure. 



The work on the part played by carbohydrates in the 

 formation of animal fat led to a keen controversy with foreign 

 investigators. Lawes and Gilbert had satisfied themselves by 



o. B. 16 



