1896.] MICROSCOPICAL JOURNAL. 171 



the blood from being given an impetus up or down when 

 blown from the end. 



According to whether the specific gravity of the blood 

 is equal to, greater, or less than that of the solution, it 

 will pursue a horizontal course, sink or rise. By trying 

 a number of solutions one may be found in which the blood 

 neither rises nor sinks, or two are found in one of which 

 it rises and in the other sinks. In the last case the 

 specihc gravity of the blood is between the two. 



In our experience with the Gowers' instrument, we 

 have found it very unsatisfactory. It is often quite im- 

 possible to get the tint of the diluted blood to correspond 

 to that of the standard one-per-cent solution. Even when 

 this is attained, a difference in shade may be produced by 

 looking at the instrument somewhat from the side instead 

 of straight from in front ; by holding the paper for re- 

 flection farther away from or nearer to the instrument ; 

 by holding the instrument between the eye and 

 the window or by moving farther away from the 

 window. In the last case, in several instances, the 

 differences produced by moving twenty feet away from 

 the source of light, was fifteen per cent, the blood 

 requiring to be more diluted when farther from the 

 window and thus giving a higher reading. These tests 

 were made in a hospital ward on a day of average bright- 

 ness. Therefore it may be seen that in addition to the 

 other sources of error, the nature of the day, whether it 

 be bright or cloudy, will make an appreciable difference. 



We have frequently disagreed in our readings of the 

 same test in both Fleischl and Gowers and others also 

 have differed from us as to when the proper shade was 

 attained. In using the Fleischl instruments, in compari- 

 son in the same cases, we have generally found a differ- 

 ence in reading between the two. In thirty per cent of 

 these comparisons the difference was as much as ten ])er 



