Hardesty, spinal Nerves of the Frog. 107 



The advantages claimed for this method of counting are 

 notably three : 



1. The method reduces the mental stain to a minimum. 

 The ordinary "net" method jused by earlier observers, and even 

 as improved by Gaule ('96), involves many difficulties which 

 are entirely avoided by the used of a photograph. 1 



2. The method is largely mechanical. The work of car- 

 rying numbers in the mind and the final addition of the num- 

 bers so carried, is transferred to the machine. 



3. The work of counting a section may be interrupted at 

 any time without the least danger of loss in the accuracy of the 

 number finally obtained. One who has ever attempted to count 

 a section containing several thousand fibers will immediately 

 realize this advantage. 



By reason of the accuracy attainable with this method it is 

 justifiable to attach great weight to the small numerical differ- 

 ences found to occur in the course of the nerve roots and trunk. 



XI. Bibliography. 



Ambronn und Held : Beitrage zur Kenntniss des Nervenmarks. II. Ueber 



Beobachtungen an lebenden und frischen Nervenfasern und die Sichtbarkeit 



ihrer doppelten Konturierung. Archiv filr Anat. und Physiol. Anat. 



Abthl. S. 214, 1896. 

 Bidder und Volkmann : Die Selbstandigkeit des sympathischen Nervensytems 



durch anatomische Untersuchungen nachgeweisen. Breitkoff und Hartel, 



Leipzig, 1842. 

 Birge, E. A. : Die Zahl der Nervenfasern und der motorischen Ganglienzellen im 



Riickenmark des Frosches. Archiv filr Anatomie und Physiologic. Phy- 



siologische Abtheilung. H. 5 und 6, 1882. 

 Bilhle, A. : Untersuchungen iiber den Bau der Nervenzellen. Verhandlungen 



der physik. med. Gesellschaft zu Wiirzburg. N. F. Bd. 31 p. 285, 1898. 

 Cajal ('90), R. y : Sur I'origine et les ramifications des fibres nerreuses de la 



moelle embryonnaire. Anat. Anz. V, p. 85, 1890. 



