March U, 1913] 



SCIENCE 



413 



nothing. The use of such an assumption in 

 most cases in the social sciences has usually 

 turned out to be an attempt to explain the 

 known in terms of the less known. 



In conclusion, it seems to me that science 

 as science may well beware of accepting as 

 yet any universal principle of explanation. 

 It can not accept such until it is demon- 

 strated. The method of science is not, as 

 some philosophers have proclaimed, to build 

 itself up upon some universal assumption. 

 Rather its methods are the pragmatic ones of 

 observation, comparison, testing by experience 

 and measurement. So far as science ap- 

 proaches exactness it is built up by the method 

 of measurement; and many other things than 

 mechanical cause and effect can be measured. 

 It is decidedly premature as yet to say that 

 science will approve any universal principle 

 or method of explanation ; and it is decidedly 

 regrettable that any one who works in any of 

 the sciences should, by a narrow definition of 

 scientific method, rule out of the category of 

 scientific works James's " Principles of Psy- 

 chology " and the whole list of important 

 contributions in the mental and social sci- 

 ences not based upon the mechanistic as- 

 sumption. Charles A. Ellwood 



University op Missouri, 

 January 20, 1913 



" MORE LITTLE BEASTS " 



To THE Editor of Science: Under the title 

 of "More Little Beasts of Field and Wood," 

 Mr. "William Everett Cram, of Hampton 

 Falls, New Hampshire, has given an account 

 of various animals met by him in his walks 

 through the woods, written in a pleasant fash- 

 ion suggestive of Thoreau, though without 

 Thoreau's touch of moral epigrams. 



It is illustrated by a number of fairly cor- 

 rect wood-cuts. 



A novel suggestion, at first sight not at all 

 convincing, is this, that the group of hares 

 and rabbits is not an off-shoot from the ro- 

 dents, but from the family of cats, a rabbit in 

 the long past being a cat, adapted perforce to 

 a vegetable diet. A good many parallelisms 

 between the cats and the rabbits are suggested, 



among others that cat flesh is sometimes sub- 

 stituted for that of rabbits in the inns of 

 Europe. David Starr Jordan 



SCIENTIFIC BOOKS 

 The Horse and its Relatives. By E. Lydek- 



KER, F.E.S. New York and London, The 



Macmillan Company. Pp. vi -|- 286 ; Pis. 



XXIV., and 11 text figs. 1912. Price $2.60 



net. 



This extremely interesting volume is a com- 

 panion to that on the ox and its kindred by 

 the same author, and summarizes most ad- 

 mirably our knowledge of the members of the 

 equine race, both living and extinct. In the 

 opening chapter the place of the horse in na- 

 ture is discussed, together with that of its few 

 surviving relatives. The eight or nine species 

 of horses, five of rhinoceroses and five or six of 

 tapirs contrast strikingly with the great num- 

 ber of artiodactyles still living. The perisso- 

 dactyles are therefore looked upon as a waning 

 race, but the cause of their diminution in 

 numbers is not yet determined. 



In discussing the structure of the horse, 

 especial emphasis is placed upon the high de- 

 gree of specialization of feet and teeth. In 

 the foot the variable degree of reduction of the 

 splint bones is of interest, the great shire 

 horse of England retaining the entire shaft 

 together with remnants of the first and second 

 phalanges of the lateral toes, all firmly welded 

 together, while the Argentine horses show the 

 greatest diminution of these bones. The 

 longheadedness so characteristic of all horse- 

 like forms is a very ancient character and 

 gives space before the eyes for the develop- 

 ment of the wonderful dental battery. The 

 pit-like depression in front of the orbit some- 

 times seen in modern horses is supposed to 

 have lodged a scent gland, of recognition 

 value, similar to that of the deer. The leg 

 callosities known as " chestnuts " are also 

 decadent skin glands. The long columnar 

 teeth with their complex infolding of enamel 

 are admirably adapted to the harsh siliceous 

 grasses which constitute the principal article 

 of diet. They are much more perfect than in 

 the cud-chewing ruminants, in which the food 



