270 SCIENCE PROGRESS 



Upon the land a far greater number of symbiotic momenta 

 could, therefore, arise and push each other on unceasingly ; 

 and the result is that it is 'upon the land that we find the most 

 developed, the most advanced, and the most intelligent animals. 

 I would point out that such notorious cross-feeders as man, 

 the apes, and the parrots, for instance, rank high in intelligence 

 and status. I believe they could never have attained to their 

 position by perpetual in-feeding. 



It is worth recalling, in this connection, that food-borne 

 infection is very common amongst animals and men, and, in 

 particular, that it is always animal food (in-feeding) which is 

 responsible for such infection. Our food-plants are not attacked 

 by any micro-organisms pathogenic to man or other animals, 

 but our animal slaves generally suffer from bacterial infection, 

 which is communicable to man. 



Again, there is the fact, established by Prof. Richet and 

 other physiologists, that fruits and vegetables — with the 

 exception of a few over-cultivated varieties — never induce 

 " alimentary anaphylaxis " (the dietary equivalent of serum 

 disease) ; whilst flesh foods often produce the same distressing 

 symptoms upon body and mind as are known frequently to 

 result from a direct introduction of unsuitable proteins into 

 the blood. 



Facts such as these I believe to be of almost inconceivable 

 importance in evolutionary physiology. They go a long way 

 in proof of the contention that nature abhors promiscuous 

 feeding, and, further, that the required specificity of the food 

 depends on the delicate and complicated relation of organisms 

 in the web of life. That is to say, the food is precisely suitable 

 only where there exists an adequately reciprocal relation 

 between supplier and supplied, and this involves cross- rather 

 than in-feeding. 



Prof. Richet interprets his results to mean that nature 

 desiderates the stability of the species. But it is also necessary 

 to recognise that, if stability is to be maintained, there must 

 exist a satisfactory bio-social basis of life, and this basis is 

 apt to vanish with any prolonged unilateral exploitation of 

 organism by organism, as in domestication, in parasitism, 

 and in merely " seasonal " Symbiosis, for instance. 



We might add the discovery that the pollen of certain 

 plants is apt to cause anaphylactic symptoms in man and 

 beast, as, for instance, in hay-fever. It appears that the deeper 

 cause of the disease is inherent in the fact of a biological 

 relation the opposite of Symbiosis between the respective 

 animals and plants. The chief culprits in the causation of 

 hay-fever have been found to be wind-pollinated (anemo- 

 philous, rather than entomophilous) plants. Prominent amongst 



