42 THE AMERICAN MONTHLY [Mar. 



only a thin layer of milk remains the tube is inclined g-ently 

 so as to expose the sediment which adheres firmly to the 

 bottom of the tube, and a small drop of it is taken and 

 spread on the cover-g-lass. This is done with a platinum 

 loop holding- 2-3 millig-rams. Several cover-g-lasses are 

 prepared in this way. Drops of cream and sediment can 

 then be examined at once for the detection of cells, foreig-n 

 bodies and motile bacteria. The other drops spread in 

 thin layers are allowed to dry, are then passed three times 

 throug-h the flame of a Bunsen burner, then left 20-24 

 hours in a mixture of equal parts of ether and absolute 

 alcohol. At the end of that time the alcohol and ether are 

 heated over a water bath to complete the extraction of the 

 fat, the cover-g-lasses are taken out, washed with absolute 

 alcohol, and are then ready for staining- by one of tire usual 

 methods. If they are stained for tubercle bacilli, the 

 Ziehl-Neelsen method is best. If the staining- be with 

 aniline dye for special purposes the film should be sub- 

 mitted first to the action of a dilute acid for a few seconds. 

 Sulphuric acid, 10 per cent is g-ood. If acid is not used, 

 the proteid matter coag-ulated on the cover-g-lass, in the 

 spaces between the fat g-lands, stains deeply, and neither 

 micro-org-anisms nor cells can be seen distinctly. This 

 permits obtaining- a permanent preparation which shows 

 clearly the number and size of the fat g-lobules. Immedi- 

 ately after preparing- the films two g-uinea-pigs are inocu- 

 lated, each with the sediment of 40 c. c. of milk. The sedi- 

 ment contained in each tube is mixed with a little of the 

 supernatant milk so as to make a total quantity of 2 c. c. 

 for subcutaneous injections, and 5 c. c for peritoneal in- 

 oculations. 



Fine Meshes. — If No. 20 miller's silk, which is reg-arded 

 as the best kind, be used to collect plankton, it is impor- 

 tant to remember that not all org-anisms are stopped by it, 

 and that while new silk lets many forms g-o throug-h, after 

 it has become clog-g-ed with diatoms, etc., less forms will 

 pass its meshes. It is not -t its best when new, and after 

 reaching- its best it begins to wear out. This sug-g-ests 

 using- a double bag- for straining- drinking water, catching- 



