viii, B, 1 Walker: Balantidicidal Activity 7 



period of time. Indeed, if the balantidicidal action was not in- 

 stantaneous or did not take place within a few minutes, the 

 substance at the given dilution has not been considered to be 

 of practical value. 



As an exarnple of these tests the following one of silver nitrate 

 is quoted from my notes: 



TESTS OF THE BALANTIDICIDAL ACTION OP SILVER NITRATE ON "BALANTIDIUM 



COLI SUIS" 



Control preparation made at 9.15 a. m. Balantidia active. 10.15, balan- 

 tidia active. 11.10, balantidia active. 



Dilution of 1 : 100 made at 9.17 a. m. Balantidia killed and fixed 

 immediately. 



Dilution of 1 : 1000 made at 9.20 a. m. Locomotion and movement of 

 cilia of the balantidia lost immediately. 9.21, extrusion of the contents 

 of the balantidia. 



Dilution of 1: 10,000 made at 9.35 a. m. Balantidia more or less 

 actively motile; 9.35i, locomotion of all balantidia have ceased; 9.36, balan- 

 tidia have collapsed and contents extruded. 



Dilution of 1: 20,000 made at 10.09 a. m. Balantidia sluggishly motile; 

 10.09 J, balantidia motionless, oral cilia motile; 10.10, the same; 10.11, 

 some of the balantidia show extrusion of small drops of protoplasm from 

 the cytostome; 10.12, more pronounced and widespread extrusion of the 

 protoplasm from both the cytostome and cytopyge of the balantidia; 10.15, 

 progressive extrusion of the protoplasm of the balantidia; 10.16, the same; 

 10.20, the same; 10.30, all balantidia have disintegrated. 



Dilution of 1:25,000 made at 10.301 a. m., balantidia actively motile; 

 10.42, the same; 10.44, some of the balantidia are nearly motionless with 

 drops of protoplasm extruding from the cytostome and cytopyge; 10.48, balan- 

 tidia sluggishly motile with large buds of protoplasm extruding from the 

 oral and anal orifices; 10.53, the same; 11.06, some of the balantidia still 

 motile; 11.39, the same. 



Dilution of 1 : 100,000 made at 9.43i a. m. 9.43, balantidia actively 

 motile; 9.45, the same; 9.52, the same; 10.00, the same; 10.34 the same; 

 11.10, the same. 



From these tests it may be concluded that silver nitrate is 

 balantidicidal to a dilution lying between 1 in 20,000 and 1 in 

 25,000. 



The results of the first series of tests of the balantidicidal 

 action of drugs and chemicals are given in Table I. In this 

 table are not included all of the experiments made nor all of 

 the dilutions tested in many of the experiments; only one 

 experiment with each substance and the critical dilutions 

 which determine quantitatively the balantidicidal activity of 

 the substance are given. 



