Thompson, Cells in the Cerebral Coi'tex of Alan. 115 



nerve cell bodies. When compared with the previous compu- 

 tations upon these two points, for which the available data were 

 comparatively incomplete, the outcome of calculations based 

 upon Hammarberg's material, is very surprising. Meynert' es- 

 timates that there are, in round numbers, 612 million nerve 

 cells in the convex surface of the cerebral cortex. This esti- 

 mate, he states, is based upon two sets of data, first, his own 

 enumeration of the cells of the various layers as they appear in 

 sections of known thickness, and second, the area of the entire 

 convex surface of the hemispheres as determined by Rudolph 

 Wagner.^ He is willing to admit a possible error of a million 

 or two in his calculation, but considers it reliable within those 

 limits. Taking Meynert's estimation as a starting point, Don- 

 aldson^ calculated that there were 1200 million nerve cells in 

 the entire cerebral cortex, and that 3000 million would be a 

 moderate estimate for the number of cells in the entire Central 

 Nervous System. The present calculation, based upon Ham- 

 marberg's data, gives the astounding result that there are over 

 9200 million nerve cells in the cerebral cortex alone, or about 

 eight times as many as the largest previous estimate.* The 

 proportion of the total volume of cortical substance composed 

 of nerve cell bodies was determined by Donaldson^ to be cer- 



1 Der Bau der Gross-Hirnrinde und seine ortlichen Verschiedenheiten. 

 Separat-Abdruck aus der " Vierteljahrschrift fiir Psychiatric etc.," 187a, vide 

 p. 18. 



^ Vorstudien zu einer wissenschaftlichen Morphologic und Physiologic des 

 menschlichen Gehirns als Seelenorgan. Zweite Abhandlung ; GSttingen, i86a, 

 vide p. 18. 



3 The Growth of the Brain. London and New York, 1895, vide p. 159. 



* Barker (The Anatomy and Physiology of the Nervous System and its Con- 

 stituent Neurones, as revealed by recent investigations. The N. Y. Med. Jour, 

 l8g7, vide p. 686, note) suggested that Donaldson's estimate of the total num- 

 ber of cells in the central nervous system was too small rather than too large, 

 because 3000 million is too small a proportion of the total number of fixed body 

 cells, estimated by Francke as 3,996,cx»o million (Die Menschliche Zelle, 1891, 

 p. 27). 



^1. c, p. 169 ff. 



