322 



Messrs. J. Mcintosh and P. Fildes. 



acid and sulphuric acid, the residue extracted with water and tested in the 

 Marsh apparatus. The technique employed was that advocated by Chittenden 

 and Donaldson (6). The rings of arsenic obtained in this way were compared 

 with a standard series of rings made from known weights of neosalvarsan, and 

 the amount of arsenic was expressed as grammes of neosalvarsan. In no 

 case was any attempt made to obtain accurate quantitative results, and our 

 figures merely indicate roughly whether a particular sample contained much 



or little neosalvarsan :— 



Gramme of 

 neosalvarsan. 



Moist brain residue after washing, 100 grm contained O004 



Supernatant fluid after fixation with brain, 500 c.c. „ O'l 



Final washing fluid „ 



Moist liver residue after washing, 100 grm „ 0'015 



Supernatant fluid after fixation with liver, 500 c.c. .. „ - l 



Final washing fluid „ 



From this experiment it appears that brain substance will fix considerable 

 quantities of neosalvarsan in vitro. 



Experiment 2. — Eepetition of Experiment 1. 



Gramme of 

 neosalvarsan. 



Moist brain residue after washing, 100 grm contained - 01 



Supernatant fluid after fixation, 500 c.c „ 0'05 



Final washing fluid „ 



Moist liver residue after washing, 100 grm „ 001 



Supernatant fluid after fixation, 500 c.c ,, 0'05 



Final washing fluid „ 



Experiment 3. — Eepetition of Experiment 1, but twice the quantity of 

 brain and liver used, viz., 200 grm. The results were similar to those 

 obtained in the other experiment, although the brain substance appeared to 

 fix more neosalvarsan than did the liver, thus : — 



Gramme of neosalvarsan. 



Moist brain residue, 200 grm. contained - 02 



Moist liver residue, 200 grm. „ 0'004 



It may be objected to these experiments, that the arsenic was merely 

 entangled mechanically with the minced tissues and was not chemically 

 fixed ; we therefore repeated the experiment after replacing the animal tissues 

 with fragments of Doulton filter (asbestos) and finest vegetable charcoal. 



