124 PATHOLOGY 



Many may consider the statement of Virchow * a witty paradox 

 when he says that the development of new species really belongs to 

 the realm of pathology, as a new species must find its origin in a 

 variation or deviation from the preceding type, and variation from 

 type is pathologic. Thus the whole teaching of evolution, the science 

 of phylogeny, is to be considered part of pathology. I share through- 

 out Virchow's opinion, and in my work on inherited and congenital 

 diseases, recently published, 2 1 have again given this fact expression 

 that we must presuppose a variability of the embryonal protoplasm 

 (Keimplasma) and that variation or deviation from the previous type 

 either acquired or inherited or even arising from external influences 

 is the necessary preliminary to the formation of a new species, sub- 

 species, or variety. I would not, however, like to go so far as to call 

 everything arising in this way pathologic, no more than I can con- 

 sider it pathologic when, by immunization, a man is made better 

 than he was before. Such a man varies from the type of normal 

 man, but is not pathologic, because the variation is useful and appro- 

 priate. Only variation which is inappropriate or useless is pathologic. 

 I realize that it may often be difficult to determine the limits of the 

 inappropriate and useless and thereby pathologic, especially in the 

 development of varieties and races. Thus, I should not hesitate to 

 class the Crested Polish fowl with its exencephalocele as pathologic, 

 while I should exclude those breeds which the animal breeders have 

 made for useful purposes from pathology, no matter how near the 

 pathologic the products of skill might be. 



Variations from type occur in inanimate as well as animate nature; 

 there are malformed crystals just as there are malformed plants, 

 animals, and persons, but we are not accustomed to speak of a patho- 

 logy of crystals or stones, but only of plant, animal, and human 

 pathology, for only with living beings can we rightly speak of useless, 

 inappropriate, or pernicious variations from the normal. 



Human pathology, undoubtedly the most momentous and import- 

 ant for us, has made but little use of plant pathology as yet, although 

 there can be no doubt that many conclusions for general pathology 

 as for general anatomy are to be drawn from botany. The reaction of 

 plant cells to unusual conditions, and the morphologic and functional 

 disturbances which occur under such circumstances are easier to 

 observe, and may well serve as guides to the understanding of similar 

 processes in animal or human cells. Experimental pathology has 

 already made use of plants in its investigations, 8 but only recently 

 have we begun to give more attention to the spontaneous diseases 



1 R. Virchow, Ra&enbildung u. Erblichkeit, in Festschrift fur Batian, 1896. 



1 Orth, Angeborene u. ererbte Krankheiten u. Krankheitsanlagen, in Krankheii 

 vnd Ehf, herausgegeben von Senator u. Kaminer. Munchen, 1904, p. 26. 



1 O. Israel, Bwtog. Studien mit Rucksicht auf d. Pathol. Virchow' Arch. 141, 

 p. 209, 1895. 



