722 



THE AMERICAN NATURALIST [Vol. XLI 



(Schafer) nor synapse (Foster) are in very wide use at present.) Gen- 

 erally, however, the book shows that the authors had in mind the 



red corpuscles of ilic hlood is M.OOO sq. meters or approximately four 

 times the size of ;i l»;is( !);,i! diamond." On the whole it is a book 

 excellemlv iidapicd to its purpose, and in its present form it can be 

 still more widelv uso<]. 



F. T. Lewis. 



ZOOLOGY 



The Nervous System of Vertebrates.^ — Bell's discovery that the 

 dorsal roots of spinal nerves in vertebrates are sensory and the ventral 

 roots motor in function may be said to be the first stej) in subdividing 

 the nervous organs of these animals into physiological regions. Tliis 

 process has been very much extended recently especially by certain 

 American neurologists witli the result that the nerves and central 

 organs of vertebrates have come to be considered as aggregations of 

 elementary systems of fillers essentially homogeneous from a ])liysi- 

 ological standj)oint. The observations upon which this conception 

 is based are contained for the most part in sjiecial pay)ers and have 

 not hcrct(^fore been collected and condensed into a single readable 

 account. Such an account has b(>en attemi)ted by Johnston in his 



standpoint, but from that of ])iiysiological compf)nenTs. Chapters 

 are devoted in sequence to the somatic afferent division as represented 

 by the nervous mechanism concerned with touch, the lateral line 

 organs, and the car; to the visccTal afferent (Hvisioti as represented by 



the cerebellum, mesencephalon, dienc<'phal()n, and cerebral lienii- 



' Johnston, J. B. The Nervous System of Vertebrates. P. Blakiston's 

 Son & Co., Philadelphia, 1906, xx + 370 pp., 180 illustrations. 



