Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . which is exactly i mm. Hence we have an area of i squaremillimeter divided into four hundred small equal squares. Through eachfifth row of squares is ruled an extra line, which is not a boundary but ismerely an aid in keeping ones position in the ruled area. Indicated, not 1 My colleague, Dr. C. C. Croy, has devised a most excellent and useful pipet attach-ment (see above cut), which prevents leakage of the contents during transportation. Thisconsists of a strong rubber band with two d
Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . which is exactly i mm. Hence we have an area of i squaremillimeter divided into four hundred small equal squares. Through eachfifth row of squares is ruled an extra line, which is not a boundary but ismerely an aid in keeping ones position in the ruled area. Indicated, not 1 My colleague, Dr. C. C. Croy, has devised a most excellent and useful pipet attach-ment (see above cut), which prevents leakage of the contents during transportation. Thisconsists of a strong rubber band with two disks of any kind of thin metal folded on the rubberin such a way that the ends of the pipet come in contact with the rubber and press against themetal disks. See, also, Saxon and Drummond, Jour. Am. Med. Assn., 1915, LXV, 1182. 458 DIAGNOSTIC METHODS. bounded, by these extra lines, the square millimeter is divided into i6 unitsof 25 small squares each (Emerson). As the ruled surface of one square millimeter is divided into 400 smallsquares, each small square has an area of 1/400 square mm. The height of. Fig. 133.—Ruled surface of Thoma-Zeiss counting chamber. (Da Costa.) the column of blood being i/io mm., the cubic contents of each small squareis 1/4000 cmm. This counting chamber of Thoma does not permit of the counting of asufficiently large number of leucocytes, especially when the dilution has beenmade in the same degree as is used for the enumeration of the red cells. Inorder to overcome this diflSiculty and also to give a larger ruled area in which
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