420 BACTERIOLOGY. 



did not destroy the agglutinating properties of typhoid 

 blood); and that in October, 1896, the serum test was 

 regularly employed in the New York Board of Health 

 Laboratory for the routine examination of the blood- 

 serum of suspected cases of typhod fever. Since then 

 numerous health departments have followed the example 

 set by those of Montreal and New York. 



USE OF DRIED BLOOD. Directions for Preparing 

 Specimens of Blood. The skin covering the tip of the 

 finger or the ear is thoroughly cleansed, and is then 

 pricked with a needle deeply enough to cause several 

 drops of blood to exude. Two fair-sized drops are then 

 placed on a glass slide, one near either end, and allowed 

 to dry. Paper may also be employed, but it is not as 

 good, for the blood soaks more or less into it, and 

 later, when it is dissolved, some of the paper-fibre is 

 apt to be rubbed off with it. The slide is placed in a 

 box for protection. 



Preparation of Specimen of Blood for Examination. 

 In preparing the specimens for examination the dried 

 blood is brought into solution by adding to it and mix- 

 ing it with about five times the quantity of water ; then 

 a minute drop of this decidedly reddish mixture is 

 placed on a cover-glass, and to it is added a similar 

 drop of an eighteen to twenty-four-hour-old bouillon 

 culture of the typhoid bacillus, which, if it has a slight 

 pellicle, should be well shaken. The drops, after being 

 mixed, should have a faint reddish or pink tinge. The 

 cover-glass with the mixture on the surface is inverted 

 over a hollow slide (the edges about the concavity 

 having been smeared with vaseline, so as to make a 

 closed chamber), and the hanging drop then examined 

 under the microscope (preferably by gaslight), a high- 



