256 Proceedings of the Royal Society of Edinburgh. [Sess. 
free from bacterial life, while in concentrations lower than this it is not 
efficient. Saturation and half -saturation are efficient in the case of salicylic 
acid. Confirmatory results have been put forth by Kikkoji (7) and 
Yoshimoto (14). These writers recommend the use of these substances in 
preference to chloroform, as the progress of digestion appears, in comparison, 
to be retarded by the latter. 
Navassart (13) and Yoshimoto (14) also give some results obtained in 
the employment of mustard oil. In all concentrations upwards from -|- 
saturation this antiseptic was apparently capable of maintaining sterility in 
the material. 
With regard to toluol, a multitude of references as to its use in various 
researches may be found, though any inquiries as to its efficiency are 
extremely infrequent. 
Hildebrandt (15) finds it possible to obtain sterility in liquids by pro- 
longed shaking with excess of toluol, and to maintain this sterility by 
covering the surface with a layer of toluol. The reliability of toluol is, 
however, questioned by Vandevelde (9), who, on this ground, throws doubt 
on the value of a considerable amount of previously published work. 
Thymol is recommended by Lewin (16) as being capable of delaying 
putrefaction in milk, egg white, and other easily putrefiable material for 
considerable periods. It has also been used to some extent by Stoclasa and 
Schittenhelm, and in the earlier researches of Vines, but in none of these 
cases is its use supported by any bacteriological evidence. Later, Kaufmann 
(6) decides, on the result of a bacteriological investigation, that thymol is 
incapable of preventing development, while Vandevelde (9) declares thymol 
to have no influence whatever on bacterial life. 
The experiments I now proceed to describe were rendered necessary 
for the purpose of the research in which I am engaged, and the present 
paper does not, of course, pretend to deal in anything like a complete 
way with this vast and important subject. It is merely a record of my 
observations. 
The investigation falls naturally into two stages, viz. : — 
1. The efficiency of the antiseptic. 
2. The influence of efficient antiseptics on enzyme actions. 
With regard to the latter part of the question, it seemed preferable to 
employ, in the experiments, such enzymes only as had been fairly well 
studied, but it is evident that the whole problem is practically inexhaustible. 
With regard to the efficiency of the antiseptics, the question may again be 
divided into two — namely, the antiseptic value in clear homogeneous liquids, 
and again, in non-homogeneous suspensions such as milk, or egg albumen, 
