No. 397-] REVIEWS OF RECENT LITERATURE. 65 
Polytomous Nerve Fibres. — Dr. E. Ballowitz! has found that the 
enormous electric nerve fibres of the electric catfish of the Nile, 
Malapterurus, do not branch as ordinary medullated fibres do, but 
divide at once into from four to nine trunks. The most usual num- 
bers were five or seven, the even numbers, six and eight, being less 
frequent. The resulting fibres varied much in calibre, but were 
always thinner than the main fibre, which, however, was not so large 
in cross-section as the derived fibres taken collectively. A derived 
single fibre may branch again dichotomously or trichotomously, as 
' ordinary fibres do. The condition shown in the division of the main 
fibre in Malapterurus is intermediate between that found in ordinary 
nerve fibres and ‘in the electric ray, Torpedo, where the branches vary 
between fifteen and twenty-five. G. H. P. 
Nerve Cells of the Human Cortex. — Helen B. Thomson? has 
undertaken some interesting computations concerning the composi- 
tion of the brain in man. She finds that the total number of func- 
tional nerve cells in the cerebral cortex of an adult man is in round 
numbers ninety-two hundred millions, and yet the volume of these is 
only 1.37% of the whole cortex. The number of giant cells in the 
cortex corresponds almost exactly with the number of pyramidal 
fibres passing to the spinal cord, and hence the pyramidal fibres are 
probably the processes of these cells. o Hb 
The Fur Seals and Fur Seal Islands. — The third volume of the 
voluminous report on the Fur Seal and the Fur Seal Islands, by Dr. 
David Starr Jordan and his associates, is just issued from the Gov- 
ernment Printing Office. The first two volumes, issued some time 
since, relate to The Fur Seal of the Pribilof Islands : its History, its 
Natural History, and its Fate. The fourth volume, already issued, 
consists of Dr. Leonhard Stejneger's report on The Fur Seal Islands 
of Russia and Japan. 
The present volume is due to the enlightened interest of Mr. 
Charles Sumner Hamlin, then Assistant Secretary of the Treasury, 
Who instructed the Commission to use all possible effort to complete 
our knowledge of the fauna and flora of the regions visited. 
The present volume of 630 quarto pages is devoted almost entirely 
! Ballowitz, E. Ueber polytome Nervenfaserteilung, Anat. Anzeiger, Bd. xvi, 
PP- 541-546. 
? Thomson, H. B. The Total Number of Functional Cells in the Cerebral 
Cortex of Man, etc., Journ. of Comp. Neurology, vol. ix, pp. 113-140. 
