140 Value of High Powers in the Diagnosis of Blood Stains. 



applicable as a liquid for moistening blood stains and bringing into 

 view the delicate cell-walls of their constituent corpuscles than the 

 75 per cent, salt solution. I can, however, fully agree with my 

 friend, Dr. E. M. Bertolet, that for preservation and prolonged 

 study of specimens of blood stains, glycerin forms the best medium 

 at our disposal, although it seems to me that his suggestion, that 

 ■we should before mounting them tint the cell-walls and nuclei 

 of oviparous blood-corpuscles with the reagents employed in the 

 admirable guaiacum test for blood, will be found in practice less 

 advantageous than my own plan of using aniline solution. And 

 this in part on account of the difficulty of procuring the ethereal 

 proportion of peroxide of hydrogen, and of applying it to micro- 

 scopic specimens, and partly because it will prove so much harder 

 to convince the average juryman that a bright blue material (instead 

 of a crimson-red substance) is actually clotted blood. 



In examining spots of blood more than one-tenth of an inch in 

 diameter, I would advise that fragments should be scraped from the 

 edges or thinnest parts of the stain, because specimens from the 

 central portions sometimes exhibit numerous fibrin filatnents which 

 have appeared before the desiccation of the drop. These of course 

 interfere with the investigation by forming a more or less complete 

 meshwork around the cell-walls, and so confusing the delicate 

 outlines which the latter present when the view is uninterrupted. 



As a contribution towards answering the question of how long 

 after their deposit upon objects blood stains may be detected by 

 microscopic investigation, I may mention that a fragment from one 

 of the twenty blood spots used in May 1869 "for estimating the 

 delicacy of the microscopic test for blood " (determined at raoo o of 

 a grain, as stated in my paper in vol. Iviii., N. S., oi the ' American 

 Journal of the Medical Sciences,' p. 57) was recently examined as 

 above described, and found still at the end of five years to exhibit 

 multitudes of corpuscles, which could be clearly distinguished from 

 those of the ox or sheep, as will be seen by the following record of 

 measurements made May 23, 1874 : — 



The corresponding average of my measurements five years ago 

 was ^^77 of an inch, so that no further contraction seems to result 



