Nuclei Tuberis Laterales and the Ganglion Opticum Basale. 3 



from one another and from the surrounding cell groups. The unfor- 

 tunate condition which here exists is present also in many other regions 

 of the nervous system, and I have considered the tendency of the anatom- 

 ical work on the mammalian brain somewhat at length not merely as 

 an interesting explanation for our present want of definite information, 

 but because this tendency contains a serious defect whose results are 

 most evident and far reaching, a defect which should be corrected. 



The tendency of neurological workers to attach little importance to 

 differences in cell character I have criticised, not only at this point but 

 also later in this article. On the other hand I have no intention what- 

 ever of disparaging the ability of other authors, nor am I unapprecia- 

 tive of the excellence, in many cases, of their work and of the valuable 

 results which they have contributed. My criticism is aimed exclusively 

 at the almost universal belief that the various differences in cell type 

 in the nervous system are, after all, of no great importance, and that 

 We should reserve our efforts to discover the connections of various 

 portions of the nervous system. It would be unfair to blame authors for 

 being influenced by a belief so general; moreover it is only compara- 

 tively recently that we have begun to employ methods capable of reveal- 

 ing the striking differences in cell character, and only in recent years 

 has the development of cytology given an added stimulus to the careful 

 study of the nerve cell. Above all I wish to disclaim any belief that the 

 method herein employed — that of setting aside groups of cells of an 

 identical type and of comparing such cell groups and of attempting to 

 discover the correlation between cell tj'pe and cell function — is of any 

 more value than many other methods of investigation. I advocate it not 

 to displace other methods, but to complement them and add to their 

 usefulness. 



Material. 



The material studied consists of the following complete series : four of 

 man, one of macacus rhesus, two of lemur rufus, and three of the cat. 

 The tissue was in each case fixed in 95 per cent alcohol, and after dehy- 

 dration and treatment with chloroform embedded in paraffin. The 

 sections were stained in a one per cent aqueous solution of toluidin blue 

 (Griibler), differentiated in 95 per cent alcohol, dehydrated in absolute 

 alcohol, cleared in xylol, and mounted in Canada balsam. 



