390 A SHORT HISTORY OF SCIENCE 



Amid all the revolutions of the globe the economy of Nature has 

 been uniform, and her laws are the only things that have resisted the 

 general movement. The rivers and the rocks, the seas and the con- 

 tinents have been changed in all their parts; but the laws which 

 direct those changes, and the rules to which they are subject, have 

 remained invariably the same. Lyell's Vol. I, Title Page Motto. 



GENERAL RESEMBLANCE OF MAN TO THE LOWER ANIMALS. 

 At the end of the eighteenth century the increase of knowledge 

 nowhere led to more startling revelations than in comparative 

 anatomy, for a very moderate amount of dissection of the various 

 types of vertebrates suffices to show that all of these, including 

 man himself, are built upon the same general plan. Similarity 

 extends even into minute details, as in the lungs, aortic arches, 

 teeth, eyes and ears, and the complex musculature of the limbs. 

 Similarity in the organs and processes of reproduction among the 

 higher animals had been recognized ever since the time of Aris- 

 totle, and the discovery of the mammalian ovum by von Baer 

 in 1827 simply added another link to the long chain of resemblances 

 between man and other higher vertebrates and the lower, such 

 as reptiles, frogs, and fishes. Embryology now strengthened this 

 chain by showing that the embryos of these various animals are 

 more alike than are the adults into which they develop thus 

 suggesting that all were originally similar or even identical, but 

 had afterwards become differentiated. Malthus in his startling 

 work on the Principle of Population had proved a tendency in 

 mankind to multiply, like other animals, without reason and 

 beyond the means of subsistence. The antiquity of man, long 

 suspected, was established by the finding, in 1854, by Boucher de 

 Perthes, of human remains along with those of extinct animals 

 in the caves of northern France. Archaeology and linguistic 

 studies had already contributed to disprove the conventional 

 chronology (which held that the creation of the world occurred 

 4004 B.C.) and thus, indirectly, the current cosmogony, by dis- 

 covery of the remains of prehistoric culture, and by showing 

 that the modern European languages and arts are evidently direct 

 and related descendants of earlier and sometimes extinct forms. 



