THE GROWTH OF GROUPS 163 



as due to some unknown morbidity nor does it appear 

 necessary to explain congenital mental disorder by any 

 such agency. Whatever the explanation may be, it is 

 probably the same in both cases. We do not know why 

 mutants appear, but if we obtain knowledge in the one 

 case it will be applicable to the other. 



The conception of disease as an entity in itself is held 

 by many physicians and alienists. For example, Lugaro 

 writes, " Every individual variety, one may even say 

 every individual, is in itself an exception to the law of 

 heredity, though to a partial and scarcely appreciable 

 extent. Variations which depend on pathological causes 

 are always markedly divergent from the normal." 



This passage contains the idea, suggested also by 

 Virchow, that all marked variations, such as hare-lip and 

 extra digits, are pathological in origin, but this suggestion 

 was first made at a time when we hardly knew anything of 

 pathological cause, before it was recognized that the 

 greater part of pathological cause was micro-organism. 

 In the present state of biological knowledge, it is unjusti- 

 fiable to say that markedly divergent variations depend 

 on pathological cause and that small variations are not 

 so dependent. The variations of organisms cannot be 

 divided into great and small, with a clear line between ; 

 they are of all sizes so to speak. 



If the present position of psychiatry is represented 

 by Lugaro in the paragraphs quoted, biology is perhaps 

 able to render it some assistance, though not of a hopeful 

 kind. 



The group of mental states gathered together by Krae- 

 pelin under the name Dementia prcecox is illustrative of 

 congenital disorder and is therefore chosen here for 



