66 THE TREND OF THE RACE 



agencies on embryonic development is the great variety of anom- 

 alies which are produced in response to any one agency. Fere's 

 interest in the causation of innate defect led him to consider the 

 problem of how development may be influenced by external 

 factors, and accordingly we find the author of the Pathology oj 

 the Emotions and various other treatises on abnormal psychology 

 and nervous disorders, writing numerous notes upon the effect of 

 all sorts of agencies upon the development of the egg of the 

 domestic fowl. Injurious agencies generally effect a retardation 

 of development and the production of various anomalies; more 

 rarely there are produced individuals defective in certain respects 

 but presenting in general a superior development. 



There is a certain parallelism between the manifestations of 

 morbid heredity and the pathological effects of injurious agencies. 

 Just as certain substances produce a great variety of teratological 

 effects in the developing embryo, so certain hereditary factors 

 result in very diverse characters in the adult organism. The 

 toxins of a chronic disease such as syphilis produce a bewildering 

 multiplicity of symptoms, and it should occasion no surprise that 

 certain inherited tendencies should do likewise. If there be 

 hereditary factors whose effect on development is to produce a 

 general retardation and deterioration after the manner of the 

 toxic influence of some chemical substance, the manifestations of 

 these factors in successive generations might take the form of 

 stigmata of degenerations as varied as those which occur in many 

 families of defective human beings. Fere speaks of such phenom- 

 ena as indicative of "the dissolution of heredity," as if we were 

 dealing with something which weakened or broke up the force of 

 embryogenic energy. Perhaps the germ plasm of certain individ- 

 uals may contain elements which tend to destroy the fidelity of 

 hereditary resemblance, although it may be questioned whether 

 this would in strictness be a dissolution of heredity. 



It is, of course, possible to maintain that the multiplicity of 

 degenerative phenomena in human beings is the result of various 

 unit factors each of which tends to produce a particular kind of 

 defect. However true this may be in regard to certain character- 



