A RESUME OF THE USES OF FORMALIN. 67 



experiments were satisfactory, but their attempt to disinfect a large 

 room did not give perfect results. They, however, demonstrated 

 the fact that layers of dust a centimetre thick were rendered sterile. 

 They also devised a portable apparatus for producing the gas. 



Alleger made quite an extensive series of experiments in order 

 to determine the germicidal action of formalin on bacteria. He 

 made use of cultures of the bacillus of diphtheria in Petri dishes. 

 The surfaces of these dishes were sprayed with solutions of forma- 

 lin varying in strength from i to 1 0,000 to 1 to 100. He found 

 that a solution of i to 2,000 prevented the growth of the bacillus, 

 but not that of moulds. Another series of experiments were made 

 with stick cultures in test tubes. Five drops of solutions of forma- 

 lin, varying in strength from i to 20,000 to i to 100, were placed 

 on the surface of the culture media in each tube. At the end of 

 forty-eight hours none of the tubes which had been treated with a 

 I to 100 or stronger solution showed any growth. A third series 

 of experiments were made with smear cultures, which were allowed 

 to grow for from twenty-four to forty-eight hours, and then they 

 were treated with the above-mentioned solutions of formalin for a 

 few minutes. Cultures were then made from these, with the result 

 that no growth took place from those treated with the stronger 

 solutions. 



Formalin has also been used in surgery, obstetrics, and gynae- 

 cology, as an antiseptic, but has had to be abandoned on account 

 of its irritating properties. As a preserving agent formalin was 

 first used by the botanists. Cohn experimented with it extensively, 

 and found that the green and red colours of plants were not ex- 

 tracted. At the end of five months his specimens still retained 

 their natural colours, and were not shrivelled. The botanists 

 Sadebeck and Holfert recommend it highly. 



It was first introduced into the zoological technique by F. Blum, 

 who obtained excellent results with it as a preservative agent, and 

 it has now come into general use. The excellent results obtained 

 by the botanists and zoologists with formalin as a preservative soon 

 resulted in its introduction into the anatomical and histological 

 technique, and at the present time it is quite generally used. As 

 a preservative agent for gross specimens, it is used in the strength 



