The Fixation of Arsenic by the Brain. 



321 



Mouriquand (3) found the brain and cord in five animal experiments to 

 be free from arsenic, although other organs contained much. They also 

 concluded that salvarsan has no neurotropic effect. On the other hand, 

 Mouneyrat (4), after the injection of salvarsan into animals, found arsenic 

 " in very appreciable quantities in the liver, muscles, and brain, distinctly 

 more than the infinitesimal amounts met with in the control animals, which 

 had had the same food but no injection." Thus Mouneyrat considered that 

 salvarsan was " particularly neurotropic." In criticism of this paper it must 

 be stated that the author gives no evidence of having made quantitative 

 estimations, by which he might have discovered that the liver and kidney, 

 for example, contained vastly more arsenic than the brain. Further, the 

 fact that he was able to demonstrate arsenic in the brains of normal 

 animals must lead to a certain suspicion of his other results. 



The observations of Ullmanu, Morel and Mouriquand and ourselves were 

 accepted by Ehrlich (5) as showing that salvarsan has no " Vorliebe " for the 

 brain. 



As a result of subsequent investigations upon the minute anatomy of the 

 cerebral vessels, however, we were not entirely satisfied that the deductions 

 we had drawn were correct. 



It appeared that absence of arsenic from the brain might be due to two 

 distinct factors. Firstly, the arsenic might not be " fixed " by the brain as 

 already suggested, or, secondly, it might not gain access to the brain, owing 

 to some peculiarity of the cerebral vessels. In order to test this possibility 

 we conducted experiments in vitro, applying neosalvarsan directly to fresh 

 brain substance, and then found that neosalvarsan was in fact " fixed " by 

 the brain. 



Experiment 1. — 100 grm. of fresh human brain and 100 grm. of human 

 liver were minced and placed in two separate glass bottles of 1000 c.c. 

 capacity. These bottles were filled with saline solution, shaken, allowed to 

 stand, and the supernatant fluid removed. The tissue was thus freed from 

 excess of blood ; 500 c.c. of saline solution, containing 0"15 grm. of 

 neosalvarsan, were then added to each, and the bottles were shaken for 

 one hour. At the end of this time the supernatant fluid was removed by 

 decantation and the bottles filled with saline solution eight times, shaking on 

 each occasion and removing the washings by decantation. By this method it 

 was hoped that all " unfixed " neosalvarsan would be removed from the 

 tissues. 



Estimations of the amount of neosalvarsan in the washed tissue, the 

 supernatant fluid after fixation, and the final washing fluid were then made. 

 In every case the material to be tested was heated with concentrated nitric 



