. The science and practice of dental surgery. ett.) smaller basio-nasal length. explaining the liigherpalatal index and the equal molar index, althoughthe molar lengths are absolutely greater. 70 The question at once arises, Is this differencean inlierited character, the result of gradualchange through successive generations, or is itsolely the result of the influence of externalconditions, diet and such like, operating duringthe lifetime of the individual? The problems of heredity have been attackedin recent years from \\idely different great generalizations of Darwin, founded
. The science and practice of dental surgery. ett.) smaller basio-nasal length. explaining the liigherpalatal index and the equal molar index, althoughthe molar lengths are absolutely greater. 70 The question at once arises, Is this differencean inlierited character, the result of gradualchange through successive generations, or is itsolely the result of the influence of externalconditions, diet and such like, operating duringthe lifetime of the individual? The problems of heredity have been attackedin recent years from \\idely different great generalizations of Darwin, foundedupon a study of the facts of variation, ofiened uplarge fields of investigation as to the extent ofresemblance between parents and children (22)(106), the material basis of inheritance, andthe reasons for the differences between anorganism and its progenitors; and the re-discovery of Mendels experiments in breedinghas stimulated a large number of workers toinvestigate on the same lines and accumulatefurther evidence in support of his laws of. Fig. 117.—Two maxillae, showing a large amount of tjaw, A, and mucli less in the larger jaw, B. (Matthew descent. It is, of course, impossible to discussthese various metiiods in detail, but it will benecessary to refer to such results as have beenobtained bearing upon the form and size ofthe jaws in man. The apjalication of Mendelianmetiiods and arguments to man is but in itsinfancy. They are primarily experimental,and the conclusions are based on the numeri-cal results of first crosses and fertilization oflike forms in succeeding generations (23) (72).The classical experiments were made with talland dwarf jjeas, in which a first cross betweentall and short always produced tall peas, butfertilization of tall by tall in the next genera-tion produced botli tall and short, and subse-quent union of short and short produced onlyshort. The quality of tallness is said to bedominant to the quality of shortness, whichis called therefore recessiv
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectdentistry, bookyear19
