2 THE AGE OF MAMMALS 



Peter Simon Pallas, Pieter Camper, and Johann Friedrich Blumenbach. 

 Pallas (1747-1811) in his great journey (1768-1774) through Siberia dis- 

 covered the vast deposits of extinct mammoths and rhinoceroses. Cam- 

 per (1722-1789) contrasted (1777) the Pleistocene and recent species of 

 elephants; Cuvier (1799) published his memoir on the living and fossil 

 elephants; and Blumenbach (1752-1840) separated (1803) the mammoth 

 from the existing species of elephants as Elephas primigenius. In 1792 

 Kerr distinguished the American mastodon as Elephas americanus. In 

 1799 Thomas Jefferson (1743-1826) described the giant American Pleis- 

 tocene sloth Megaloriyx} 



The ancient life of the Atlantic border of North America was also 

 becoming known through the pioneer work of Richard Harlan (1796- 

 1843), Jeffries Wyman (1814-1874), and Joseph Leidy (1823-1891). The 

 master works of Joseph Leidy began with the first fruits of western explora- 

 tion in 1847, and extended through a series of grand memoirs, culminating 

 in 1874. Leidy adhered strictly to Cuvier's exact descriptive methods, 

 and while he was at heart an evolutionist and recognized clearly the genetic 

 relationships of the horses and other groups, he never indulged in speculation. 



Cuvier's Law of Correlation. — As a means of escaping the difficulties 

 caused by the imperfections of fossils, Cuvier formulated and announced his 

 famous 'law of correlation.' He reposed in this law a buoyant confidence 

 which subsequent experience has shown to have been largely misplaced. 

 He replied to the critics of the new science of palaeontology, who deplored the 

 imperfect nature of fossils, that the comparative anatomist does not require 

 the entire animal, because certain laws of invariable association enable him to 

 predict from a single part the structure of other parts. Thus, he observed, 

 we are establishing supposititious laws which become almost as certain as the 

 laws of reasoning, so that now any one who sees the track of a cleft foot 

 may conclude that the animal which left it is ruminant; and this assertion 

 is as sure as any other in physics or morality. This footmark alone gives 

 to the observer both the formation of the teeth, the shape of the jaws, 

 the structure of the vertebrae, and the form of all the bones of the legs, 

 thighs, shoulders, and even the frame of the animal which has passed. 

 It is a more certain mark than all those of Zadig.- 



None of the numerous and genuine scientific discoveries of the great 

 Frenchman brought him such immediate prestige as did this famous law. 

 In reference to it Balzac said at the time that Cuvier "rebuilt like Cad- 

 mus cities, from a tooth"; yet, although in part defended by Huxley,^ 

 there is more error than truth in this law as Cuvier conceived it, for there 



' Jefferson, Thomas, A Memoir on the Discovery of Certain Bones of a Quadruped of 

 the Clawed Kind in tlie Western Parts of Virginia. Trans. Amer. Pliilos. Soc, Vol. IV, 1799, 

 pp. 246-260. 



^ The above paragraph is a literal translation from Cuvier's Discoura. See full title, p. 1. 



* Huxley, On the Method of Palseontology. Ann. Nat. Hist., Vol. XVIII, 1856. Scien- 

 tific Memoirs, 1898, Vol. I, pp. 436-4:59. 



