OF DENISON UNIVERSITY. ^7 



tions mounted in balsam. Several hundred such sections were pre. 

 pared and studied by the method of geometric reconstruction from 

 camera drawings and measurements. 



The chrom-acetic solution appears to us to have decided advan- 

 tages over any other fluid used. For some brains it should be consid- 

 erably more dilute than the standard advised by Fol. The most gen- 

 erally satisfactory stain is aqueous haematoxylin with the possible ex- 

 ception of a new stain, an account of which is at present reserved. 

 Alum-cochineal ranks next and, although it does not preserve the fine 

 histological details and causes a shrinking of cells and delicate organs 

 generally, it has the great advantage of being adajjted for the staining 

 of fragments in toto, thus enabling one to fix the sections ujmn the 

 slide at once, obviating the danger of loss as well as avoiding the great 

 labor mvolved in the usual haematoxylin method. The ordinary car- 

 mine stains are relatively useless as are the alcohol solutions of haema- 

 toxylin, etc. 



Analine blue-black has many of the good proj)erties of haematoxylin 

 but seems less desirable on the whole. A solution of methyl blue in 

 oil of cloves promised well, but it was found impracticable in actual 

 practice. So far as our experiments w^ent the mingling of stains with 

 Mueller's fluid proved unsatisfactory. 



In some cases alum-cochineal serves to differentiate the fibre tracts 

 very perfectly, but those preparations are less perfect resi)ecting the 

 cells. In fact no reagent was found serving both purposes etjually. 

 We have preferred, therefore, the use of a reagent which alters the 

 natural relations as little as possible and permits the tracing of what 

 may be confidently regarded as the normal connections albeit at great 

 expense of patience and time. Successfully stained haematoxylin i>rcp- 

 arations do this. The various methods of staining fibres only, although 

 undoubtedly of the highest value, do not prove adajned for the minu- 

 ter work of tracing cells in their mutual relations. Ours has been the 

 common fate. It has not infrequently hapi^ened that the same process 

 applied to two entirely similar brains has resulted in failure in one 

 case and success in another. Thus far no infallible technitpie has i)een 

 discovered. The statements made on the basis of the few specimens 

 studied must remain 0])en to the criticism of subsecpient study. 



Previous to the sectioning, as already said, several localization ex|)er- 

 iments were made both by electrical stimulation and extirpation. The 

 first specimen was a male of Arctomys nwiuix, the same specimen which 



