LIFE: ITS NATUEE, OBIGIN AND MAINTENANCE 33 



has been prepared synthetically, and when their exact chemical nature 

 has been somewhat better elucidated it will probably not be difficult to 

 obtain others in the same way. 



From the above it is clear that not only is a co-ordination through the 

 nervous system necessary in order that life shall be maintained in a 

 normal condition, but a chemical co-ordination is no less essential. These 

 may be independent of one another ; but on the other hand they may 

 react upon one another. For it can be shown that the production of 

 some at least of the hormones is under the influence of the nervous 

 system (Biedl, Asher, Elliott) ; whilst, as we have seen, some of the 

 functions of the nervous system are dependent upon hormones. 



Time will not permit me to refer in any but the briefest manner to 

 the protective mechanisms which the cell-aggregate has evolved for its 

 Protective chemical defence against disease, especially disease produced 

 mechanisms. Toxins by parasitic micro-organisms. These, which with 

 and antitoxins. ew exce ptions are unicellular, are without doubt the 



most formidable enemies which the multicellular Metazoa, to which all 

 the higher animal organisms belong, have to contend against. To such 

 micro-organisms are due inter alia all diseases which are liable to become 

 epidemic, such as anthrax and rinderpest in cattle, distemper in dogs and 

 cats, small-pox, scarlet fever, measles, and sleeping sickness in man. The 

 advances of modern medicine have shown that the symptoms of these 

 diseases the disturbances of nutrition, the temperature, the lassitude or 

 excitement, and other nervous disturbances are the effects of chemical 

 poisons (toxins) produced by the micro-organisms and acting deleteriously 

 upon the tissues of the body. The tissues, on the other hand, endeavour 

 to counteract these effects by producing other chemical substances 

 destructive to the micro-organisms or antagonistic to their action : these 

 are known as anti-bodies. Sometimes the protection takes the form of a 

 subtle alteration in the living substance of the cells which renders them 

 for a long time, or even permanently, insusceptible (immune) to the action 

 of the poison. Sometimes certain cells of the body, such as the white 

 corpuscles of the blood, eat the invading micro-organisms and destroy 

 them bodily by the action of chemical agents within their protoplasm. 

 The result of an illness thus depends upon the result of the struggle 

 between these opposing forces the micro-organisms on the one hand 

 and the cells of the body on the other both of which fight with 

 chemical weapons. If the cells of the body do not succeed in destroy- 

 ing the invading organisms it is certain that the invaders will in the 

 long run destroy them, for in this combat no quarter is given. For- 

 tunately we have been able, by the aid of animal experimentation, 

 to acquire some knowledge of the manner in which we are attacked 

 by micro-organisms and of the methods which the cells of our body 

 adopt to repel the attack, and the knowledge is now extensively utilised 

 to assist our defence. For this purpose protective serums or anti- 



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