664 journal of Comparative Neurology and Psychology. 



The first group of anatomists works from the standpoint of 

 developmental mechanics, the nervous masses being considered 

 as shaped more or less passively by surrounding growth forces or 

 by internal pressures and strains due to irregularities in the growth 

 of the masses themselves. The second group lays the emphasis 

 rather upon the functional nervous tissue itself as the determining 

 factor in cerebral morphology. 



An excellent illustration of the methods of the mechanical school 

 is furnished by some of the embryological papers of the late Pro- 

 fessor His, particularly his figures showing very clever mechanical 

 models of the invagination of the neural plate, formation of the 

 neural tube, etc.^ 



As applied to comparative neurology this standpoint received its 

 clearest exposition and most graphic illustration at the hands of 

 Professor Rudolf Burckhardt, whose untimely death last 

 winter interrupted in the midst an exceedingly valuable series of 

 researches. In a personal letter written last January a very few 

 weeks before his death he outlined the motives of his work in these 

 words: 



"The principal point — besides the fact that never such large 

 materials have been examined before — is for me that all our views 

 of the central nervous system are still dominated by practical, 

 psychological, physiological, traditions, and that the simple stand- 

 point of vertebrate phylogeny has never been thoroughly kept, 

 as by observing such objects as growing epithelia which are 

 changed by influences of head-formation, and the central need 

 of sensory organs (the latter has been urged most by Johnston). 

 Second, that brain phylogeny must be studied according to 

 phylogeny as it issues from palaeontological researches. You will 

 perhaps miss that I do not enter into description of fiber courses, 

 but only into their quantity as a mechanical factor; that I treat 

 the nerve cells as such as of secondary value for the knowledge 

 of brain genesis and the type of the brain, and that on the other 

 side I attribute such a high value to neuroglia. But you will 

 also see that I wanted to regard the brain as a part of the head, and 

 the real head, not the hypothetical of primary metamerism, which 

 for the brain has not much more value than for the skin. There 

 is, in my opinion, a great field for work, particularly for zoologists, 



' His, Wm. Ueber mechanische Grundvorgange thierischer Formenbildung. Arch. f. Anat. [u. 

 Physiol.]. 1894. 



