60 



different compounds of the same element, will throw much light on 

 its relations with other bodies. And when brought in contact with 

 other substances as reagents, we may arrive at a knowledge of its 

 properties. Such considerations induced him to experiment on the 

 properties of the elements of the living organism, by bringing these, 

 while still forming part of the living animal, into contact with certain 

 reagents derived from inorganic compounds. He submits a tabular 

 view of the experiments, and deduces from them the conclusion that 

 the reactions which take place between the elements of living beings 

 and inorganic compounds, differ from what would be expected from 

 a consideration of the ordinary chemical properties of the reagents 

 employed. 



But his results are not merely of a negative character. They 

 point out a new law, that when the ordinary properties appear to 

 lose their application, a new and more latent property of matter 

 comes into play. The substances he has experimented with divide 

 themselves into groups, each distinguished by peculiar reactions. 

 Potash and ammonia agree in their phenomena. So of strontia, 

 baryta, and lead, which influence the muscular system. Soda and 

 silver agree very closely in their phenomena. A large family of 

 substances, including lime, magnesia, zinc, iron, copper, manganese, 

 nickel, and cadmium, produce similar effects, being distinguished 

 from all other bodies by their action on the nervous system. Tla- 

 tinum, palladium, iridium, and osmium, agree in their reactions. 

 Phosphorus, arsenic, and antimony, form a group. Sileninm and 

 sulphur act alike; as do chlorine, iodine, and bromine. These groups 

 correspond with the chemical arrangement, according to isomorphous 

 relations. Hence the law deduced, "that the physiological action 

 of these substances depends upon some property they possess in 

 connection with these isomorphous relations." 



The exception to this law in the separation of soda and silver from 

 the potash group, is only apparent: "for while the isomorphous 

 relations between soda and silver are well marked, and also between 

 potash and ammonia, it still admits of doubt, whether any well 

 marked relations exist between the first two and the last two sub- 

 stances." 



It will be seen from the table that the substances least injurious 

 are those which exist in the body, or have isomorphous relations with 

 some of its constituents, and the reverse. It will also be perceived, 

 that there is a Avant of agreement between the chemical and physio- 

 logical action of substances; an acid and alkali sometimes produce 



