THE BLOOD. 175 



At this point the attention of the student will be directed to 

 but two instruments: (1) the Thoma-Zeiss apparatus, and (2) the 

 Daland haematocrit. 



1. THOMA-ZEISS APPAKATUS. The apparatus consists of two 

 separate and distinct parts: a capillary tube and a counting cham- 

 ber. The tube is for the purpose of measuring the amount of blood 



Fig. 50. Hsemacytometer of Thoma-Zeiss. (LAHOUSSE.) 



A, Capillary glass tube. B, A glass slide upon which is a covered disc 

 accurately ruled so as to present 1 square millimeter divided into 100 squares 

 of a/ao millimeter each. 1, Blood is drawn up to this point. 101 represents 

 normal saline-solution drawn up the tube, mixed with the blood drawn up to 

 1. In 101 parts the blood forms 1 part. 



whose corpuscles are to be, counted. By it also is accomplished the 

 proper dilution in the upper, bulbed chamber. The capillary por- 

 tion of the tube is graduated to 0.5 and 1.0 marks. Just above the 

 capillary portion of the instrument is the bulbous portion contain- 

 ing a small glass ball to assist in the thorough mixing of blood and 

 diluting normal saline fluid. Just above the bulb is the 101 mark. 

 For drawing both blood and the diluting saline into the apparatus 

 there is attached a piece of rubber tubing with a suitable mouth- 



