806 



SCIENCE 



[N. S. Vol. XXX. No. 779 



D. VON Hansemann. Pp. 488; no illustra- 

 tions. Berlin, A. Hirschwald. 1909. 

 There is considerable room for doubt 

 whether the title of this fascinating volunie 

 was well chosen and whether a more correct 

 title would not be " Evolution and a Pathol- 

 ogist " instead of " Evolution and Pathology." 

 But, while there is little pathology, as such, 

 the subject matter is presented by a master 

 mind whose training has been in the field of 

 abnormalities, and many a well-worn bio- 

 logical theme is clearly illustrated by facts 

 from his own domain of science. In his intro- 

 duction von Hansemann states that his book 

 is for those who are familiar with the prin- 

 ciples of evolution, but who have no far-reach- 

 ing knowledge of pathology; and for those 

 pathologists who have been so absorbed in 

 pursuing their own goddess that they lack in- 

 sight into the subject-matter of modern evo- 

 lution. It would be expected, therefore, and 

 the expectation is fully realized, that the es- 

 sential points in the philosophy of evolution 

 vpould be presented in the clear light of a well- 

 trained mind and by one who views them 

 somewhat objectively. 



A vigorous supporter of Darwin, von Hanse- 

 mann pays his respects to neo-vitalists by 

 calling their philosophy pure speculation, and 

 as such really less scientific in spirit than 

 that of the old nature philosophers (p. 8), and 

 throughout the book he returns again and 

 again to the dicta of Darwin and of Weis- 

 mann. The chapters on Preformation, 

 Species and Varieties, Variability, Conditions 

 of Constancy, Altruism, Design (Zweck- 

 massigkeit) and Orthogenesis, Lamarckism, 

 Functional Adaptation, Epidemics and Phys- 

 iological Death, are devoted mainly to argu- 

 ments in favor of the origin of variations. 

 While much of this matter is old and many of 

 the arguments somewhat hackneyed to a 

 biologist, there is, nevertheless, a constant 

 novelty in the ever-present point of view of 

 the pathologist and a not inconsiderable orig- 

 inality in the interpretation of facts. Here, 

 especially, are to be noted his views on vari- 

 ability, on altruism, on regeneration and 

 transplantation, and on epidemics. 



The key-note of his view on variations is 

 sounded in the sentence " die ganze Frage- 

 stellung in Bezug auf die Entstehung der 

 Variabilitat eine unrichtige ist" (p. 150), 

 and he takes the original ground that vari- 

 ability is one of the fundamental properties of 

 living protoplasm and seeking for its origin, 

 therefore, is lost effort. If a constant tendency 

 to vary is a fundamental property of proto- 

 plasm, then the problem of the origin of 

 species becomes more simple by the effort to 

 ascertain what it is that gives or causes con- 

 stancy of type. The chapter devoted to this 

 phase of his subject (Bedingungen der Kon- 

 stanz) is the most interesting one in the book 

 and is worked out with the greatest argumen- 

 tative ingenuity and with a wealth of illus- 

 trations and citations. Concerning variabil- 

 ity he says: 



Natiirlich stelle ich mir diese innere Ursache 

 nieht als irgend etwas Mystisches vor, das aus- 

 serhalb der mechaniachen Erklarungsmoglichkelt 

 liegt, sondern als eine der lebenden Materie in- 

 harente physikalische Eigenschaft, die aus der 

 besonderen Form der Vereinigung ihrer Atome 

 und Molekule erklart werden muss und deswegen 

 zur Definition der lebenden Substanz gehort (p. 

 152). 



As a ball upon an inclined plane is pre- 

 vented from rolling by some external hin- 

 drance, so species, having an inherent and 

 continual tendency to vary, are prevented 

 from changing by reason of external condi- 

 tions. Adaptation means the establishing of 

 an equilibrium between the internal forces 

 and such external conditions. The statement 

 of his principle is followed by a discussion of 

 the many ways whereby constancy of type 

 might be brought about, environmental and 

 climatic changes, inheritance and other phe- 

 nomena usually credited with bringing about 

 variations, are here regarded as effective 

 agents in checking the inherent tendency to 

 vary, while in the highest types of living 

 things, which presumably have passed through 

 a long phylogenetic history of variations, this 

 fundamental property has become weakened 

 or partially lost, so that in such highest forms 

 we find the greatest fixity of types. 



The phenomena of regeneration, also, are 



