. Evolution and its relation to religious thought . ndition in herbivores being an extreme modi- PEOOFS FROM HOMOLOGIES. 99 fication associated with another modification mentionedunder 5. 4. In man and in many mammals, and in all reptilesand birds, there are two bones in the forearm (radiusand ulna). In the more spe-cialized forms of hoofed animals(ungulates), such as horse andruminants (Figs. 8, 9), there isapparently but one. Two is thenormal and original number;but one of them, the ulna, hasgradually become smaller andsmaller, and finally is reducedto a short splint, and consoli-dated with
. Evolution and its relation to religious thought . ndition in herbivores being an extreme modi- PEOOFS FROM HOMOLOGIES. 99 fication associated with another modification mentionedunder 5. 4. In man and in many mammals, and in all reptilesand birds, there are two bones in the forearm (radiusand ulna). In the more spe-cialized forms of hoofed animals(ungulates), such as horse andruminants (Figs. 8, 9), there isapparently but one. Two is thenormal and original number;but one of them, the ulna, hasgradually become smaller andsmaller, and finally is reducedto a short splint, and consoli-dated with the radius as a pro-cess extending backward to formthe j)oint of the elbow. In thehorse family every step of thisreduction and consolidation maybe traced in the course of itsgeological history. 5. The ivrist of many mam-mals and all birds differs instructure from that of man,chiefiy in containing a smallernumber of bones. The normalnumber, as in man, seems to beeight. The decrease takes placemainly by consolidation of two or more into one. In such. 100 EVIDENCES OF THE TRUTH OF EVOLUTION. cases usually the embryo will show the bones still separate,thus revealing the ancestral condition. Again, the posi-tion of the wrist is noteworthy. In man, monkeys, thebear family, and several other mammalian families, andin all reptiles, the hand bends forward at the wrist, sothat the tread is on the w^hole palm (palmigrade). But,in all the most specialized mammals, the wrist can notbend in this direction, and therefore this joint can not bebrought to the ground. The tread is therefore on thetoes (digitigrade), and the wrist is high up above theground. In the horse (Fig. 9), the ox, and many othermammals, for example, the wrist is so high that it isnot usually recognized as a wrist, and is often calledthe fore-hnee. ISTow, homologous parts ought to havethe same scientific name; but to use the word ^liand^^in the case of lower animals might produce confusionand misconception. Therefore it has
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Keywords: ., bookauthorlecontej, bookcentury1800, bookdecade1880, bookyear1888
