IV. VISCOSITY MEASUREMENTS 



111 



sets of tubes are filled from the right end up to the zero marks. Then 

 the same suction is applied to both sets of tubes by means of the bulb 

 G. When the blood reaches mark 1 (or 3^ or 2) in tube M2, the suc- 

 tion is cut off, and the position of the water meniscus in tube Mi is 

 read. The numbers on tube Mi, which is wider than tube M^, repre- 

 sent volumes of water in the same units as do the numbers on tube 

 M2. If the blood in tulje il/2 is at mark 1, the number at the water 

 meniscus in tube Mi is the relative viscosity. Further details of 

 technique may be found in an article by Bircher {10). 



Fig. 1. The Hess viscometer (after Barr, 3). 



For clinical studies, no pressure gage is necessary, but if tests at 

 different rates of shear are desired, the apparatus can be equipped with 

 an air reservoir and a gage. 



D. VISCOSITY OF PROTOPLASM 



Occasionally, protoplasm occurs in rather large masses and it is 

 possible to obtain quantities of living substance that can then be ex- 

 amined in the same way that any fluid can be studied. Thus, the 

 protoplasm of slime molds can be obtained in sizable drops and these 

 drops can then be forced through a capillary viscometer. This was 

 done by Pfeiffer ill). Pfeiffer also studied protoplasm squeezed out 

 of cells of the alga Chara, although in this case the protoplasm must 

 have been mixed with cell sap. In the case of the squid giant nerve 

 fiber, the protoplasm readily flows out when the fiber is cut. Such 

 protoplasm can also be forced through a capillary tube, and, in this 

 way, the viscosity can be studied. Some preliminary studies in this 

 direction were made by a former student of mine, Mr. L. Nelson, but 

 nothing has as j^et been published. Undoubtedly, when prot()])lasm 

 is squeezed out of the cells in which it normally occurs, it undergoes 



