Page:Popular Science Monthly Volume 71.djvu/133

Rh general methods of the past and the doctrine of special creation; inheriting, on the other hand, the new spirit and contributions of Vesalius, Cesalpino, Ray and many others, and building upon this the foundations of modern botany and zoology.

In attempting to appraise Linnæus's contributions to the broader knowledge of the class of mammals, we must bear in mind what Dr. J. A. Allen has well shown, namely, that Linnæus was primarily a botanist, that his interest in mammals was incidental, his opportunities for studying them very limited and his first-hand knowledge of extra-European mammals practically nil; and finally that several of his ordinal groupings of mammals (e. g., rhinoceros with the rodents) now appear highly unnatural and even ludicrous. But there are certain considerations which may prevent us from thinking any the less of Linnæus's judgment and genius on that account.

Although Linnæus may have known very little about extra-European mammals, he had, nevertheless, a fairly good conception of the essential features of mammals as a class, as shown by his definition in the tenth edition of the "Systema Naturæ" (1758). Here in concise phrase he states 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," i. e., with flesh, as opposed to the "naked" jaws of birds; that the penis is intromittent. the females viviparous, that they secrete and give milk, that the channels 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 very few 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).

Many of these characters had previously been noticed by Ray in his description of the hairy quadrupeds: and it is not impossible that Linnæus may have been assisted to the comprehension of the essential features of the mammals through his friendship with Bernard de Jussieu, who is said by Isidore Geoffroy St. Hilaire to have induced him to include the Cetaceans in the class Mammalia; and possibly he owed something to the researches of Klein and Brisson. But Linnaeus's own studies in medicine, in Holland, doubtless made him familiar with the anatomy of at least one mammal, man, and on his journeys through the north of Europe he must have observed many mammals at close range.

All this prepared him for the clear recognition and emphasis of two facts of far-reaching importance. It was evidently well known