in the Diagnosis of Blood Stains. 133 



from experiments upon the gigantic blood-disks of the Menobran- 

 chus, in which crystals of haemato-crystalhn were seen to prop 

 out a visible membranous capsule). Indeed, as I have elsewhere 

 remarked, if the red blood-globules are simply homogeneous lumps 

 of jelly-like matter, the chance of discovering any individual cor- 

 puscles in a mass of dry blood-clot, however moistened, seems 

 almost as hopeless as the search after individual^ rain drops in a 

 cake of melting ice. 



Notwithstanding this, however, we find in the third edition of 

 Prof. A. S. Taylor's work on Medical Jurisprudence,* figures of red 

 blood-corpuscles of ten difierent animals, as they appear under a 

 low power, with the statement (strictly accurate in regard to blood- 

 disks thus feebhj magnified) that " there are no certain methods of 

 distinguishing, microscopically or chemically, the blood of a human 

 being from that of an animal, when it has been once dried on an 

 article of clothing." This declaration seems to show that more 

 complete and conclusive proof is still needed of the superior advan- 

 tage derivable from the application of high objectives to the diagnosis 

 of blood stains. 



The a iwiori arguments against the value of this microscopic 

 test for distinguishing human blood from that of the ox, pig, horse, 

 sheep, and goat, may be grouped under three heads, viz. : — 1st. It 

 is objected, as by Taylor, Caspar, and others, that the diflerence 

 between the red blood- corpuscles of man and of these domestic 

 animals, is too minute to render their positive discrimination 

 possible, and too insignificant to admit of its being used as the 

 means of condemning a fellow-creatm-e to death. 2nd. That even 

 if the average diameters of these various corpuscles were shown to 

 be so difierent that we might sometimes by this means distinguish 

 them, yet the variations above and below the mean diameter are so 

 frequent and irregular, that they must render the determination of 

 any such averages by mere micrometric measurement unreliable ; 

 and 3rd, many mvestigators believe, with Virchow and Briicke, that 

 no microscopist can "hold himself justified in putting in question a 

 man's life on the uncertain calculation of a blood-corpuscle's ratio 

 of contraction by drying." 



In reply to the first of these objections, it may be urged that 

 the blood-corpuscles are just as much characteristics of the difierent 

 kinds of hving beings in which they occur, as are the coverings of 

 the body, the shape of the legs, or the number of joints in the 

 antennae, so that exactly as we may tell, for example, a bird's skin 

 from an animal's, by the former being covered with feathers, whilst 

 the latter is furnished with haii', so we may distinguish a bird's or 

 a camel's blood from that of a man, by the former having oval cor- 

 puscles, whilst those of the latter are rounded in their outhne. 



* Vol. i., p. 548. 



