vtii.] THE CHEMISTRY OF LIFE. 87 



obtain their food from chemical manufactories, and to be 

 independent of the vegetable world ; and this appears as 

 far beyond possibility as it wovild be to create or destroy 

 matter or energy by any physical process. 



The truth on this subject appears to be, that the albu- 

 minoid class of substances, which are those which appear 

 most essential to the vital processes of both animals and 

 vegetables, can only be formed in, and by, an organism ; 

 and that those so-called organic products which have been 

 made in the laboratory are not capable of forming part of 

 any living tissue, but are only products of the decompo- 

 sition of living tissue.^ I do not say that they are all 

 waste products. Urea, which was the first organic com- 

 pound that was made in the laboratory, is no doubt a mere 

 waste product. But this is not true of butyric ether, the 

 flavouring matter of the pine-apple; amylic ether, the 

 flavouring matter of the pear ; and formic acid, which is 

 produced by ants.^ These have all been made in the 

 laboratory, and yet they are not waste products : on the 

 contrary, they are stored in the organism for piirposes con- 

 nected with its economy. But they are not capable of 

 forming part of any living tissue. The truly organic com- 

 pounds — those, I mean, which constitute the substances 

 in which the vital processes go on — are colloidal, or gela- 

 tinous. Formic acid and the ethers, on the contrary, 

 belong to the crystalloidal^ class of substances, which may 

 be solid and may be liquid, but cannot assume the inter- 

 mediate gelatinous form ; and though many of these, as 

 for instance water, are necessary to life, they cannot be- 

 come part of any living tissue — in a word, they cannot 

 be vitalised — unless they enter into combination, and in 

 so doing change their character. 



1 See Dr. Beale's edition of Todd and Bowman's Physiology, p. 9. 



^ See Quarterly Journal of Science, Jan. 1866, p. 36. 



^ I do not mean tliat they have been crystallized. But this is not the 

 only test of crystalloidal nature. Only crystalloids have a strong flavour of 

 any kind ; and strong flavour is a chai'acteristic of the substances mentioned 

 in the text. This property is no doubt a result of tlieir diflusibility in 

 water, by reason of which they are able, when in solution, to come in 

 contact with the extremities of the nerves of taste. 



