274 



Mr. A. W. Blytb. 



[Nov. 26 



Whatever their significance may be, they were for this particular 

 sample of excreta distinctive, and moreover had such a special manner 

 of growth that they could be readily recognised by the unaided sight, 

 so that their presence or absence in the succeeding experiments could 

 be easily noted. 



The disinfectants first experimented upon were some in common 

 use, such as ferrous sulphate, cresol, and potassic permanganate. 



Ferrous Sulphate. — To the 0'5 per cent, typhoid water crystals of the 

 sulphate were added and allowed to remain at the ordinary tempera- 

 ture for twelve hours, crystals at the end of that period were still 

 undissolved, so that in effect the solution was saturated. 



Of this liquid a quantity equal to 125 mgrms. of the original typhoid 

 stool was taken for cultivation. Growth was rapid ; at the end of 

 three days fifteen colonies were counted, composed of common 

 liquefying bacteria and bacilli ; besides these, there were sixty-five 

 others which did not liquefy the gelatine, i.e., within the same time, 

 among which were to be found both kinds of the light brown bacilli 

 above described. The total number of colonies calculated per gram of 

 the original typhoid matter, which had escaped destruction, were thus 

 640. 



Cresol. — The crude carbolic acid of commerce, so largely used for 

 disinfecting purposes, is a mixture of phenol and cresol with small 

 quantities of other tar principles. The cheapest carbolic acid may be 

 considered impure cresol, all phenol that the manufacturer can 

 possibly crystallise out having been removed ; hence in the following 

 experiments with Calvert's cresol some information is obtained as 

 to the value of the disinfection of typhoid matters as ordinarily 

 performed. 



An exact 1 per cent, solution of cresol was made in typhoid water, 

 and drops weighed out, at the end of fifteen minutes, three hours, 

 and twenty-four hours respectively. 



The number of colonies per gram of the original typhoid matter 

 appearing at the end of four days' cultivation was as follows : — 



No. of colonies per gram 

 of typhoid matter 

 taken. 



Cresol acting for 15 minutes 89 



„ ,, 3 hours .... 27 



24 „ .... 8 



The brown colonies were not detected in the last cultivation, but 

 were present in the others. 



The experiments were next extended to the amines and to the 

 pyridine series, substances, the action of which on Bacterium termo 

 and on sewage had already been studied. 



