312 SYMBIOGENESIS 



danger of a non-reciprocal foreign substance becoming 

 dominant (prepotent) can only be met by a supreme effort of 

 the " Land-sturm " above referred to. 



Prof. Richet states that in anaphylactising substances 

 we are not dealing with pure homogeneous products, but rather 

 with mixed substances. 



Obviously when using horse serum we are using a very complex 

 substance. Congestines obtained from actinaria, from Hura crepitans, 

 although more homogeneous, are nevertheless mixtures of very similar 

 substances which it will be found difficult to separate. 



Evidently we are here dealing with substances that are far 

 too complex to be valuable, and, what is less obvious but rather 

 more important, with substances that are biologically inade- 

 quate. On the one hand such substances introduce much 

 foreign material difficult to get rid of, and, on the other hand, 

 their ingestion must frequently lead to deficiency diseases ; 

 more pronouncedly so when through direct injection into the 

 blood the defensive forces of the digestive tract are put out of 

 action and rendered useless. An animal uses up the valuable 

 ingredients derived from plant food in its own life-processes, 

 and its serum must contain decomposition products difficult to 

 break down further, and vitamines, if at all, robbed of some of 

 their constituents. What is human blood to do with such fare 

 except to protest against its intrusion? 



Prof. Richet makes certain very tentative suggestions as 

 regards the possible composition of these sera, and he thinks 

 that Bio-Chemistry will probably enlighten us one day as to 

 the real properties of the various groups of albuminous sub- 

 stances here concerned, i.e., "Bio-Chemistry will have the 

 final word in the matter." 



It seems a fair inference that we are here dealing, how- 

 ever, with a general and biological inadequacy, and that it is 

 in reality Bio-Economics that will have the final word in the 

 matter. We are also justified in inferring that the whole case 

 of serum-disease confirms my oft-repeated bio-economic dictum 

 that Nature abhors perpetual in-feeding. Indeed, the 



