B.— CHEMISTRY 67 



Group 2. 



Dimethyldodecylbenzylammonium chloride . 



Decane-i : io-Z)w (benzyldimethylammonium chloride) . 



Decane-i : lo-bts (benzyldiamylammonium chloride) 



Group 3. 



Lauramidine ........ 



Sebacamidine ........ 



Decane-i : lo-diamidine ...... 



Group 4. 

 ^-pP-Tetrabutyldiaminoethoxybenzene 

 /)-PJ3-Tetra-amyldiaminoethoxybenzene 



In considering the results of the foregoing tests, it must be recollected 

 that there is a large margin of error, and in the results given previously 

 we have quoted the minimum concentrations found lethal in a number of 

 tests ; in the case of compounds which appeared promising we have 

 usually carried out six or more tests. In our hands, the test of Laidlaw, 

 Dobell and Bishop easily distinguished between compounds in the ' peak ' 

 area and those at each extremity, but comparison between the members 

 of a series near the peak of efficiency was difficult. This fact may be 

 illustrated well by reference to the table (see p. 69) recording the direct 

 comparison of the amoebicidal properties of tetra-n-butyl- and tetra-w- 

 amyl-diaminoalkanes. 



As the result of the foregoing experiments ax-tetra-n-amyldiamino-«- 

 decane (T.A.D.D.) was selected for further study. The conditions of 

 all the amoebicidal tests described above were those most favourable for 

 emetine, that is, in a faintly alkaline medium. It is well known (Laidlaw 

 and others ; Henry and Brown, 1923) that the exceedingly high efficiency 

 of emetine in vitro, of the order of i in 5,000,000, is only found in alkaline, 

 neutral or only very faintly acid media. Our results afford abundant 

 confirmation of this fact. When endeavouring to assess the value of an 

 amoebicide in the treatment of amoebic dysentery by comparison with 

 emetine in vitro it appears therefore necessary to consider carefully the 

 hydrogen ion concentration likely to be met with in the areas infested with 

 amoebae. 



We have been unable to find any reference to the actual hydrogen ion 

 concentration in the amoebic ulcer, but Knowles and others (1923) found 

 that the pH of a number of stools containing motile amoebae averaged 

 6-22. They also reported the results of experiments on kittens artificially 

 infected with E. histolytica in which the colon and rectum of the animals 

 were minced in saline and the hydrogen ion concentration of the sus- 

 pension determined. The average ^H value obtained in these experi- 

 ments was 6-33, and the livers when similarly treated showed an average 

 ^H value of 6-34. 



Furthermore, a considerable amount of work has been carried out upon 

 the reaction of living, dead and diseased body cells, and the work of 

 Rohde (1927) and Chambers and others (1927) suggests that the contents 

 of the ulcers may have a hydrogen ion concentration more acid than 

 pU 7-0. 



