398 Froceedings of Royal Society of Edinhurgli. [june 18 , 
enougli. We believe that it is not generally realised that a paper 
so prepared can he used as a measure of the alkali present, and, by 
having a sufficient series of these papers, that it is possible to test 
the strength of a solution of caustic potash or of any other alkali. 
We determined, therefore, to test blood with a series of papers 
coloured by litmus, plus varying quantities of an acid, such as 
oxalic. By experiment we determined the amount of acid which 
was required to prepare a red litmus paper which gave, and only 
just gave, a reaction with normal blood. Two or three other 
stronger papers were then prepared; these of course only giving 
reactions with blood that was abnormally alkaline. In the same 
way several weaker litmus papers, containing little acid, were 
prepared ; these gave reactions with blood less alkaline than normal. 
In order to estimate the strength of the litmus papers, they were 
tested with a solution of caustic potash of known strength. Although 
it is sufficient to glaze the litmus papers, yet we found that if, in 
addition, they were dipped in liquid paraffin oil for a second or two, 
and then dried, even better results were obtained. When a drop of 
blood is placed upon the paper so prepared sufficient of the plasma 
passes into its substance to affect the litmus. The corpuscles, how- 
ever, can readily be washed away, after which the reaction, if any, 
is at once apparent. We have worked with a series of seven or 
eight papers — the first in the series made with very little oxalic 
acid, the second with more, and so on. We are able in this way 
certainly to obtain a rough idea of the amount of alkali present, and 
this with a single drop of blood. The blood is obtained by pricking 
the finger after it has been carefully cleansed. A litmus paper of 
medium strength is moistened with the drop, and this is washed 
away after an interval of ten seconds. This is effected by dipping 
the paper in distilled water, and then pressing it between the folds 
of neutral blotting paper. If the blood gives a reaction, a stronger 
paper is tried ; if it gives no reaction, we try a weaker one. After 
one or two trials the blood will, let us suppose, give a reaction with 
the sixth, but not with the seventh paper. It is known that a - 
X 
solution of an alkali will give the same reaction, and therefore the 
7h 
alkalinity of the blood will be - • It is probable that this latter 
