28 Bulletin American Museum of Natural History. [\'ol. XX^'II, 



f)f the mammfe as a class character and from his felicitous coinage of the 

 word "mammalia" ^ as a class name for the forms characterized by Ray as 

 "viviparous hairy animals." Thus the terrestrial hairy quadrupeds and the 

 Cetaceans were for the first time united under a single class name. This 

 had already been foreshadowed by Ray and by Bernard de Jussieu (fide 

 I. Geoffroy, 182G, p. 66). Nevertheless, the recognition of afhnity under- 

 lying obvious external differences was one of the points in which Linne often 

 excelled, and the present instance was one of several in which he traversed 

 "common sense" and tradition to good effect. 



As Dr. Gill (1907, p. 491) has recently expressed it, "Popular prejudice 

 was long universal and is still largely against the idea involved. Sacred 

 writ and classical poetry were against it. It seemed quite unnatural to 

 separate aquatic whales from the fishes which they resembled so much in 

 form and associate them with terrestrial hairy quadrupeds. How difficult 

 it was to accustom one's self to the idea is hard for the naturalist of the present 

 day to appreciate. Linnaeus himself was not reconciled to the idea till 1758, 

 although Ray had more than hinted at it more than three score years before. 

 At least, however, in no uncertain terms he promulgated it. It was a triumph 

 of science over popidar impressions; of anatomical consideration over 

 superficial views." 



The definition of the term "INIammalia" shows that Linnaeus had a fairly 

 good conception of the essential features of the class. In concise phrase 

 he states or clearly implies (1758) that mammals have a heart with two 

 auricles and two ventricles, with hot red blood; that the lungs breathe 

 rhythmically; that the jaws are slung as in other vertebrates, but "covered," 

 /. e., with flesh, as opposed to the "naked" jaws of birds; that the penis is 

 intromittent; that the females are viviparous, and secrete and give milk; 

 that the means of perception are the tongue, nose, eyes, ears and the sense 

 of touch; that the integument is provided with hairs, which are sparse in 

 tropical and still fewer in aquatic mammals; that the body is supported on 

 four feet, save in the aquatic forms, in which the hind limbs are said to be 

 coalesced into a tail (the only erroneous idea in the whole definition). 



It had evidentlv long been well known that the anatomv of mammals 

 was similar in plan if not in detail to that of man; and we find Descartes, 

 for example, in his 'Discourse on Method' (Part V., 1637) advising those 

 who wished to understand his theory of the action of the lungs and circula- 

 tory system, "to take the trouble of getting dissected in their presence the 



1 According to Gill (1902, p. 434) the name "Mammalia" was made in analogy with well 

 known Latin words like "animal," "capital," "feminal" and "tribunal," and tlie form was prob- 

 ably suggested by animal ("that which breathes"); hence "mammal," that which possesses 

 breasts. 



