138 



0)1 the Value of High Powers 



sion lens (giving an amplification, with the A eye-piece, of 12" 

 diameters), a fragment of the blood stain was soon discovered, which 

 displayed the delicate cell-walls of its component red and white 

 corpuscles, as figured in my ' Handbook of Medical Microscopy,' 

 p. 284. Ten consecutive red disks from these, selected simply as 

 among those which had become but little distorted, were found to 

 measure as noted below in the first column. The second and third 

 rows of figures show the result of similar experiments, performed 

 on samples 2 and 3, all the magnitudes being given in parts of an 

 English inch. 



Since the red corpuscles of human, ox, and sheep's blood 

 measure, according to Gulliver, -zioo, toVt, and g-gVo- of an inch 

 respectively, and previous experiments of my own had demonstrated 

 a disposition to slight contraction in the corpuscles of blood stains 

 which have been dried and moistened again, I of course concluded 

 that sample No. 1 was human blood, No. 2 was ox blood, and 

 No. 3 was sheep's blood. On reporting these diagnoses to Prof. 

 Eeese, I had the satisfaction of learning that they were " entirely 

 correct." 



Careful examination of the three specimens furnished me by 

 Dr. Mitchell, and prepared in a manner similar to that detailed 

 above (except that diluted liq. iodinii comp. was used instead of 

 aniline liquid for tinting the cellular elements), led me to analogous 

 conclusions, as will be seen from the following table of measure- 

 ments : — 



