536 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



ganesc, arsenic, sodium, lime, or ch;ii-coal powder, and man}?^ other 

 substances, Avjint the vohitile disinfecting power; iodine, bromine^ 

 nitrous acid, and some other bodies are too dear, or are entirely 

 volatile, or are injurious to the cattle. On full consideration, it 

 appears that the choice must lie between chlorine, ozone, sulphur, 

 and the tar acids (carbolic and cresylic). Two of these bodies,. 

 viz: chlorine, in the shape of chloride of lime and the tar acids^ 

 have the great advantage of lieing both liquid and aeriform; they 

 can be at once added to discharges, and constantly diffused in the 

 air. All these four substances — chlorine, ozone, sulphurous acid, 

 and the tar acids — have been practically tested, either in England 

 or on the Continent, and there is considerable evidence that they 

 all actually do destroy the cattle plague poison. Their precise 

 mode of action is still uncertain. Chlorine and ozone act, no 

 doubt, as powerful oxidisers, converting animal poiso-ns into sim- 

 ple and innocuous substances. Sulphurous acid probal^ly destroys 

 the virus by its strong antiseptic powers. The tar acids, accord- 

 ing to the experiments of Mr. Crookes, neither interrupt nor 

 accelerate oxidation, but they act most powerfully in arresting all 

 kinds of fermentative and putrefactive changes, and annihilate 

 with the greatest certainty all the lower forms of life. After a 

 full consideration of the relative merits of the four disinfectants, 

 and after some practical trials, Mr. Crookes arrived at the conclu- 

 sion that the must powerful, and at the same time most simple 

 process of disinfection, Avould be to use the tar acids as constant 

 liquid and aeriform disinfectants, and sulphur in the form of sul- 

 phurous acid a;; an additional and occasional agenc}^ 



In our first report we recommended both these agents in a state 

 of combination; the best mode of using them in a free state will 

 be found detailed in Mr. Crookes' report, and in the instructions 

 which we furnished to your Majesty ^s Government in February 

 last, and which will be found in the appendix. The general result 

 of the experiments on disinfection with carbonic acid and sulphur 

 is certainly very encouraging. For the details of these experi- 

 ments, which have been careful and searching, we refer to Mr. 

 Crookes's report. It is of course most desii-aWe that no ftilse 

 hopes should be raised, for we have seen but too many instances 

 in which a rude disappointment has utterly crushed what seemed 

 reasonable expectations. But no one can peruse the account of 

 what has been done without seeing that a fair case has been made 

 out for a large and systematic trial of these measures. They must, 



