in the Diagnosis of Blood Stains. 139 



From these results, I of course decided that No. 1 was ox blood, 

 No. 2 was sheep's blood, and No. 3 was human blood, and on 

 reporting my conclusions to Dr. Mitchell, I was again very much 

 gratified to receive a reply informing me that they were perfectly 

 correct. 



It is interesting and important to observe, that in no instance 

 do the minimum diameters of the human blood-corpuscles closely 

 approach the maximum diameter of even those from ox blood. It 

 is true that corpuscles are occasionally to be met with both in fresh 

 blood and in dry clot, which fall much below the general average 

 of the specimen, but these are comparatively rare (not amounting 

 to over one in a hundred), and they so generally in fresh blood 

 bear such marks of traumatic injury or pathological change, that it 

 is only fair to disregard them in making up our estimates. If my 

 views are correct respecting the osmotic processes constantly going 

 on through the cell-wall of both the red and the white corpuscles,* 

 alterations in the specific gravity of the hquor sanguinis, surround- 

 ing the corpuscles, produced by desiccation at the margin of the 

 thin glass cover, must cause slight changes in the diameter of the 

 disks. Nevertheless, as these variations necessarily lie between 

 their normal size (g^^Vs ?)> and their magnitude when dried upon 

 a slide (axV 2 ?)j they can never lead to confusion in diagnosis even 

 from ox blood. 



In regard to the practical minutiae of the examination of 

 blood stains, I have little to add to the description given a page 

 or two back, except concerning the menstrua advised by various 

 authors. 



The saturated solution of sulphate of soda recommended by 

 Prof. Charles Kobin, and endorsed by numerous authorities, has the 

 disadvantage of rapidly crystallizing around the specimen, and 

 must, I think, owe its popularity chiefly to the fact that it often 

 contains large quantities of a peculiar fungus, the spores of which 

 closely resemble red blood-corpuscles both in size and general 

 appearance, and have, I doubt not, frequently been mistaken for 

 blood-cells. Diluted albumen and solution of hypophosphite of 

 soda have not in my hands seemed to possess any peculiar ad- 

 vantages, and the method of Erpenbeck, quoted by Prof. Taylor, 

 of gently breathing on the fragments of blood-clot until they are 

 sufficiently moistened to liquefy, will not, I believe, in general 

 enable us to demonstrate any corpuscles except the leucocytes of the 

 coagulum. These leucocytes have probably often been mistaken by 

 observers for " decolourized red disks." 



The highly refractive properties of glycerin and its solutions 

 advised by Dr. Taylor and others, render it in my judgment less 



* Vide ' Report on the Structui'e of the White Blood-corpuscle,' " Trans, of 

 Am. Med. As^oc," 1872, p. 178. 



