19, 3 Mazwell: Filariasis in China 267 
distinct blue. The white corpuscles take the dye; the red 
corpuscles remain unstained. In this work a mechanical stage 
with parallel movement is quite indispensable. If it is wished 
to prepare permanent specimens of filariz, a patient should be 
selected in whose blood there are many embryos. A very thin 
preparation of blood should be taken and fixed with alcohol 
or heat. The hemoglobin is washed out by water acidulated 
with a little acetic acid; the specimens are stained with any 
stain that may be wished and are mounted permanently in 
balsam. For single stains, hematoxylin or methylene blue are 
very good, while for double staining hematoxylin and eosin 
make a good combination. 
I have already stated that the staining should be done as - 
soon as possible. It is possible to leave the slides in a dry 
place for months and yet get a satisfactory result, but the 
removal of the hzmoglobin becomes more difficult, and the 
specimen does not stain well. It need hardly be said that, 
in taking the blood, due care must be taken. The needle or 
lancet must be carefully sterilized, and the skin of the part from 
which the blood is to be drawn should be cleaned first with soap 
and water and then with spirit. If this is done, there are never 
any unpleasant effects following. 
The acetic acid concentration method of Smith and Rivas ° 
is of great use in giving a quantitative estimation of micro- 
filarize in the blood. 
The method is as follows: 
From 0.1 ec. to 1.0 cc. of blood is taken from the finger and collected 
in 5 cc. of a 2 per cent acetic acid solution for the purpose of laking the 
blood. The mixture is shaken gently for several minutes and then centri- 
fuged and spreads are made from the sediment. 
Lynch * used 1 cubic centimeter of blood in 10 cubic centi- 
meters of 2 per cent acetic acid solution, centrifuged, washed 
and recentrifuged several times, spread the sediment on a slide 
and counted the whole number in the sediment. 
During 1902 Gulland(15) suggested the possibility of the 
diagnosis of filariasis from a differential count of the leucocytes 
in the blood of the patient. He pointed out that filariasis is 
accompanied by a leucocytosis proportional to the number of 
‘For this method, which works very well, I am indebted to Sir Patrick 
Manson. sae 
* Smith, A. J., and Rivas, D., Notes upon human filariasis, Am. Journ. 
Trop. Dis. and Preventive Med. 2 (1914) 368. 
*Lynch, K. M., Filarial periodicity, Journ. Am. Med. Assoc. 73 (1919) 
760. 
