- 416 - 



XXXIV. 



Animal physiology, chiefly in regard to nutrition, growth and 

 fattening. Animal Chemistry. Feeding and fattening expe- 

 riments. Breeding and Selection. 



Prof. G. C. BOURNE. Animal Cheniism: Enzymes and Hormones. 



The British Association at Sheffield, Section D., Zoology. 

 Abs. Nature, No. 2134, September 22, 1910, p. 382. 



The following is an extract from this important address: 

 " It is, perhaps, too sweeping a generalisation to assert that the 

 life of any given animal is the expression of the sum of the acti- 

 vities of the enzymes contained in it, but it seems well established 

 that the activities of cells are, if not wholly, at all events largely, 

 the result of the actions of the various kinds of enzymes held in 

 combination by their living protoplasm. These enzymes are highly 

 susceptible to the influence of physical and chemical media, and 

 it is because of this susceptibility that the organism responds to 

 changes in the environment as is clearly illustrated in a particular 

 case by Tower's experiments on the production of colour changes 

 in potato-beetles. Bayliss and Starling have shown that in lower 

 animals, protozoa and sponges, in which no nervous system has 

 been developed, the response of the organism to the environment 

 is effected by purely chemical means. In protozoa, because of 

 their small size, the question of coadaptation of function hardly 

 comes into question ; but in sponges, many of which are of large 

 size, the mechanism of coadaptation must also be almost exclusi- 

 vely chemical. Thus we learn that the simplest and, by inference, 

 the phyletically oldest mechanism of reaction and coordination is 

 a chemical mechanism. 



" In higher animals the necessity for rapid reaction to external 

 and internal stimuli has led to the development of a central and 

 peripheral nervous system, and as we ascend the scale of organi- 

 sation this assumes a greater and greater importance as a coor- 

 dinating bond between the various organs and tissues of the body. 



