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THE POPULAR SCIENCE MONTHLY. 



mind act3 first upon body, or body upon 

 mind. This M. Kibot declines to discuss. 

 Voluntary attention originated after the ear- 

 liest period of savagery, when man realized 

 the alternative of perishing or going to work. 

 It differs from the spontaneous form in that 

 the motive or influence producing the emo- 

 tional state is supplied from without. Edu- 

 cators make use of fear, sympathy, and cu- 

 riosity, to cultivate attention in the child; 

 as it advances in growth, duty, emulation, 

 and ambition are introduced; and, finally, 

 voluntary attention is maintained by habit 

 and organization A study of the internal 

 mechanism shows that attention is accom- 

 plished by inhibition. In the normal state 

 of consciousness, sensations, images, ideas 

 come and go. Attention arrests this process 

 and inhibits all but the chosen series. Ener- 

 gy is used to perpetuate this condition, and 

 from this expenditure results the feeling of 

 effort. The morbid cases of attention are 

 treated under the heads Hypertrophy of 

 Attention, Atrophy of Attention, and Con- 

 genital Infirmity. They prove that atten- 

 tion depends upon emotional excitation. In- 

 cidentally, M. Ribot gives some suggestive 

 examples of what may depend upon full 

 recognition of the physical nature of at- 

 tention. 



The Extermination of the American Bison. 

 By William T. Hornaday. Washington : 

 Government Printing-Office (Smithsonian 

 Institution). Pp. 548, with Plates and 

 Maps. 



Mr. noRNADAY is a naturalist and taxi- 

 dermist by profession, and is superintendent 

 of the Xational Zoological Park, thus com- 

 bining qualifications which well fit him for 

 making a book of this kind. He is, further- 

 more, a writer who knows how to interest 

 the reader, and has composed an attractive 

 as well as an instructive book. His purpose 

 is to help the public fully to realize the folly 

 of allowing all our most valuable and inter- 

 esting American mammals to be wantonly 

 destroyed, as the buffalo has been. The 

 wild buffalo is practically gone forever; and 

 it is doubtful whether the institution of pre- 

 serves and the formation of herds, however 

 intelligently they may be executed, will avail 

 to save the species permanently, even in a 

 captive state. In the first part of his work 

 the author considers " the life-history of the 



bison," under the headings of Discovery 

 of the Species, Geographical Distribution, 

 Abundance, Character, Habits, Food, Men- 

 tal Capacity and Disposition, Yalue to Man- 

 kind, and Economic Value to Western Cat- 

 tle-Growers. The story of extermination is 

 related in the second part. One of the most 

 important chapters in the first part is that 

 in which the value of the bison is estimated 

 under domestication, in hybrids, and as a 

 beast of burden. At present (May 1, 1889), 

 "although the existence of a few widely 

 scattered individuals enables us to say that 

 the bison is not yet absolutely extinct in a 

 wild state, there is no reason to hope that a 

 single wild and unprotected individual will 

 remain alive ten years hence. The nearer 

 the species approaches to complete extermi- 

 nation, the more eagerly are the wretched 

 fugitives pursued to the death wherever 

 found." While the herds, which once ranged 

 over nearly the whole of our country, for- 

 merly numbered hundreds of thousands of 

 individuals, the few groups that are left 

 count only dozens. An estimate made on 

 the 1st of January, 1889, gave the whole 

 number running wild — in all North America 

 — as 635 ; and including those in captivity 

 and those under Government protection in 

 Yellowstone Park, the whole number of in- 

 dividuals of the species as 1,091 ; and these 

 few are still hunted, and shot when found. 



Handbook of Practical Botany. By E. 

 Strasburger. Edited from the German 

 by W. Hillhouse. Second edition, revised 

 and enlarged. New York: Macmillan & 

 Co. Pp. 425. Price, $2.50. 



This volume embodies a course of labora- 

 tory work laid out by a botanist whom the 

 English editor calls "one of the greatest 

 living masters of microscopical observation." 

 The introduction tells how to use the micro- 

 scope, and describes the instruments of dif- 

 ferent makers. The first subject for study 

 is the structure of starch of different kinds. 

 A list of the material wanted is given at the 

 head of the chapter ; the appearance which 

 each kind of starch should present under the 

 microscope is described, its behavior under 

 various reagents is noted, and directions for 

 drawing the grains are given. The following 

 lessons are similar in character. Among the 

 subjects for investigation are movements 

 of protoplasm, epidermis and stomata, the 



