846 



SCIENCE. 



LN. S. Vol. XXIV. No. 62ft. 



The study of comparative neurology has 

 always been regarded as difficult, often as 

 uninteresting and sometimes as unprofitable. 

 However much we may ameliorate the first 

 of these difficulties by improved pedagogic 

 devices, we can not hope to make much prog- 

 ress in this direction until the stigma implied 

 in the second and third is eliminated. The 

 mere descriptive anatomy of the nervous sys- 

 tem is truly uninteresting and, like any other 

 uncoordinated mass of intricate detail, rela- 

 tively unprofitable. Only in so far as the 

 nervous system can be described in terms of 

 its functions has its study any value from 

 any point of view; and it is in respect to just 

 this correlation that the past literature of 

 neurology (both text-books and monographs) 

 has been notably weak. 



The technique of modern neurological re- 

 search is so very difficult and diversified and 

 the mass of intricate anatomical detail which 

 must be carried in mind during the progress 

 of investigation so vast, that the neurologists 

 have not, as a rule, been able to control their 

 anatomical findings physiologically as the work 

 progressed. Though anatomical research nor- 

 mally precedes physiological, yet the gap be- 

 tween them can not properly be left so wide 

 as neurologists have been inclined to leave 

 it. Even in pathology, though a few years 

 ago there was a vigorous movement toward a 

 correlation of anatomical and clinical observa- 

 tion, yet the results were disappointingly 

 sterile, and now the tendency is to lay more 

 emphasis on clinical work alone, leaving 

 anatomical research to be cultivated apart by 

 specialists in that field. This surely is not a 

 creditable situation. And though it would 

 doubtless be unjust to place the responsibility 

 on any one specialty alone, yet clearly the 

 anatomists must carry their full measure. 

 Eor it should frankly be recognized that, 

 though neurology has contributed much to 

 physiology, psychology and psychiatry, yet the 

 direct positive help given to these sciences is 

 not at the present time commensurate with 

 the vast accumulation of laborious research 

 represented in our literature of neurology. 

 And this is particularly true of comparative 



neurology, which should logically lead in prac- 

 tical fruitfulness. 



Professor Johnston's manual strikes at the 

 root of this evil. It is a text-book of func- 

 tional neurology. The unit of his descrip- 

 tions is the functional system of neurones^ 

 that is, the aggregate of related neurones 

 which cooperate in the performance of any 

 given type of reflex movement. The analysis 

 of these functional systems is a matter of 

 extreme difficulty, involving the collective use 

 of various refined anatomical and physiolog- 

 ical methods, but it is obviously so much 

 easier in the brains of lower vertebrates than 

 in the human brain that the comparative 

 method has been here most fruitful. After 

 four introductory chapters, Johnston devotes 

 himself in the remainder of the book to an 

 exposition of the functional divisions of the 

 vertebrate nervous system and their phylo- 

 genetic history. The style is direct and clear 

 and the illustrations numerous, so that the 

 student who is equipped with an elementary 

 knowledge of vertebrate anatomy and embry- 

 ology should be able to follow the author, even 

 though his method and subject matter are for 

 the most part distinctly different from those 

 of the other text-books in general use. 



Chapters five to thirteen include the defini- 

 tions and tabulation of the functional systems, 

 followed by a detailed description of each and 

 its phylogeny. Chapters fourteen to nine- 

 teen follow with a similar exposition of the 

 structure and evolutionary history of the cen- 

 ters of correlation, including the cerebellum, 

 mid-brain, thalamus, fore-brain and neo-pal- 

 lium. These fifteen chapters taken as a whole 

 constitute the most ambitious attempt which 

 has yet been made to elaborate a phylogeny 

 of the vertebrate nervous system. At no time 

 previous to this could such an endeavor be 

 expected to yield more than a limited measure 

 of success ; but by basing his phylogenies upon 

 functional units of internal structure instead 

 of superficial external features the author has 

 succeeded in demonstrating the unity of plan 

 of the vertebrate nervous system with grati- 

 fying completeness and in showing that this 

 plan is unexpectedly simple. All of the im- 

 portant known stages in the evolutionary his- 



