. The science and practice of dental surgery. opedarches, and the marked attrition of the teeth. (Half natural size.) {Museum of the RoyalCollege of Stirgeons of EiuiUind.) of useful facts, as soon asmeans have been devisedfor accurate measurement. The immediate jiroblemto be considered is: As-suming for the sake ofargument that the com-paratively small size of thejaws at the present dayis an inlierited quality, inwhat way can the diminu-tion be explained ? Muclidisctission has centredround the question of thepossibility of the inherit-ance of acquired charac-ters, that is to say, of acharacte
. The science and practice of dental surgery. opedarches, and the marked attrition of the teeth. (Half natural size.) {Museum of the RoyalCollege of Stirgeons of EiuiUind.) of useful facts, as soon asmeans have been devisedfor accurate measurement. The immediate jiroblemto be considered is: As-suming for the sake ofargument that the com-paratively small size of thejaws at the present dayis an inlierited quality, inwhat way can the diminu-tion be explained ? Muclidisctission has centredround the question of thepossibility of the inherit-ance of acquired charac-ters, that is to say, of acharacter acquired as theresult of external influenceduring the lifetime of theindividual. Much of this discussionhas been in relation to theinheritance of disease, be-cause it is difficult tounderstand in many caseshow a useless or harmfulcharacter, which is appar-ently inherited, should beperpetuated, except as theresult of external influ-ences. It is impossible to discuss this question at length, but theLamarckian hypothesis of the inheritance of. Fig. US).—Side view of same. Brachyeeplialie and On liogiiathoiis. Note theattrition of the teeth. (Half natural size.) propounded and elaborated the theory thatinfluences affecting the soma cannot produce a heritable result on the germ-cellsfrom which the next generation is derived ; butit should be clearly understood that this meansonly that a condition correspondincj to anyacquired modification of a particular part, asthe result, for instance, of use or disuse, cannotbe inherited. Weismann fully admits the effectof external conditions, such as temperature,on the germ-cells, and discusses very fully suchresults in the case of certain butterflies. In fact,Weismann considers that nutrition (using theword in a wide sense) of the germ-cells is theprime origin of the variations made use of innatural selection, and that similar minutefluctuations in a large number of the elementsof the germ-plasm are or may be accumulatedin the next generati
Size: 1621px × 1541px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectdentistry, bookyear19
