CORTICAL CKLL LAMIXATIOX OF PAPIO KAMADKYAS. 615 



select a few cells for staining, but show them complete with 

 dendrites and axon, and may enable one to truce for a con- 

 siderable distance the pnth oF the latbei-, in some cases even 

 as far as its terminal arborisation. 'J'hese nietliods are of 

 great importance, and throw light on the relations of one cell 

 to another within a pHriicalar cortical »rea, and thus on the 

 individual functions of the different types of cell. They are, 

 however, unsuitable for the survey of the arrangement of the 

 cells in their several layers, which is uecessary in order to 

 divide the cortex into regions accordino- to the tvpe of cell 

 lamination present in each. For this purpose it is necessary 

 to employ a method of a third type, such cis that of Nissl, in 

 which every ceil is i-endei'ed visible by tlie stain. Nissl's 

 method shows the general shape of each cell and its principal 

 dendrites, also the structure of the nucleus and the arrane-e- 

 ment of the extra-unclear chromatin; it does not show the 

 axon nor the nerve-fibrils running thiongli the body of the 

 cell. 



It is a variation of Xissl's methylene- bine which has been 

 used for the purposes of the present p^ipei-, namely Unna's 

 polychrome methylene-blue, as the particular point dealt with 

 is the arrangement of the layers. Much work of the kind 

 has been done on the human brain, without, however, exhaust- 

 ing the subject, but the other Primates have been somewhat 

 neglected. Of the few pa])ers dealing with them the earliest 

 is that of Schlapp (' Arcliiv f. Psychiat.,' Bd. xxx), " Der 

 Lebenbau der Gross linn rinde des Affen Macacus cyno- 

 mologus." Schlapp does not go into any great detail : 

 three types only of cortex are described and somewhat 

 roughly figured, their extent being shown by a sketch of the 

 lateral surface of the hemisphere. 



Campbell (' Histological Studies on the Localisation of 

 Cerebral Function,' Cambridge, 1905) describes the brains 

 of the chimpanzee and orang-outang. This work, which fills 

 a volume of considerable size, deals principally with the 

 hunmn brain, and treats the subject with praiseworthy 

 thoroughness. Xot only is tlie arrangement of the cells 



