A HISTORY OF SCIENCE 



the moment become quite oblivious to the special asso- 

 ciations that have to do with geography, natural his- 

 tory, and the like. But does histology give any clew 

 to the way in which such isolation may be effected ? 



Attempts were made to find an answer through con- 

 sideration of the very peculiar character of the blood- 

 supply in the brain. Here, as nowhere else, the ter- 

 minal twigs of the arteries are arranged in closed 

 systems, not anastomosing freely with neighboring 

 systems. Clearly, then, a restricted area of the brain 

 may, through the controlling influence of the vaso- 

 motor nerves, be flushed with arterial blood while 

 neighboring parts remain relatively anaemic. And 

 since vital activities unquestionably depend in part 

 upon the supply of arterial blood, this peculiar arrange- 

 ment of the vascular mechanism may very properly 

 be supposed to aid in the localized activities of the 

 central nervous ganglia. But this explanation left 

 much to be desired in particular when it is recalled 

 that all higher intellection must in all probability in- 

 volve multitudes of widely scattered centres. 



No better explanation was forthcoming, however, 

 until the year 1889, when of a sudden the mystery was 

 cleared away by a fresh discovery. Not long before 

 this the Italian histologist Dr. Camille Golgi had dis- 

 covered a method of impregnating hardened brain tis- 

 sues with a solution of nitrate of silver, with the result 

 of staining the nerve cells and their processes almost in- 

 finitely better than was possible by the methods of 

 Gerlach, or by any of the multiform methods that other 

 workers had introduced. Now for the first time it be- 

 came possible to trace the cellular prolongations defi- 



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