LABORATORY MANUAL OF PHYSIOLOGY. 



moved by the wheel (T), which fits into a rack on its lower surface. 

 The scale may be read through a small opening (m) in the plate. 

 Into the large circular opening of the plate, fits a cylindrical metal 

 cell (M) with a glass bottom and divided by a thin metal partition 

 into two equal parts. One of these halves lies over the wedge and 

 is filled with distilled water. The other contains the solution of 

 blood to be tested. The apparatus is usually supplied with three 

 cells (M, M f , M"). Of these, the first two are used in estimating 

 the haemoglobin according to Miescher's modification of v. 

 FleischPs original method. These cells are furnished with a glass 

 cover (D), having a groove which fits on the partition of the cell. 

 Over this cover is placed a diaphragm (Bl), with a longitudinal 

 slit, which permits the central part, only, of each side of the cell to 

 be seen. The third cell (M") is for use with the original method. 



Procedure. Blood from the w r ound is sucked up into the grad- 

 uated pipette (Mel) until it reaches the mark | or or y. A one- 

 per-cent solution of sodium carbonate is then sucked in until the 

 upper mark is reached. The pipette is then well shaken in order 

 to mix the blood thoroughly. One-half of the two cells (M, M'), 

 which are respectively 12 and 15 mm. high, are then filled with the 

 mixture, the other half being filled with water. The cells should 

 be completely filled. The cover glasses and diaphragm are then 

 applied and the cells are ready for examination. Artificial light is 

 employed. One of the cells is placed on the plate and the wheel 

 (T) turned until the colors of the two halves exactly correspond. 

 The result is then read off through the scale opening (m). This 

 should be repeated several times with each of the cells and the 

 average of the readings taken. The result obtained with the 12 

 mm. cell is to be multiplied by f to bring it up to that of the larger. 



Suppose the result of several readings to be as follows: 



With the large cell (15 mm.) 54-oo 



With the small cell (12 mm.) 42.00 



If the readings with the large cell are exactly correct, the reading 

 with the smaller one should be 43.2, since 54 Xf = 43.2. Or, if 



