1883.] 



MICROSCOPICAL JOURNAL. 



175 



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Microscopical Evidence Con- 

 cerning Blood Corpuscles. — From 

 reports which have come to us through 

 the newspapers, we have very meagre 

 knowledge of the circumstances under 

 which a gentleman, well-known to the 

 readers of this Journal, has testified 

 in a recent trial, that certain spots 

 found upon a coat were produced by 

 human blood. The evidence given, 

 as we have learned from the published 

 reports, was of a nature to influence 

 the result of the trial, and as it seems 

 to have been of a very positive nature, 

 we must presume that the- attendant 

 circumstances were such as to fully 

 justify it ; for, at the present time, it 

 seems rash, to say the least, to venlure 

 very positive testimony founded upon 

 measurements of blood corpuscles 

 alone. In other words, if, in the case 

 referred to, it were conclusively shown 

 that the stains could not have been 

 produced by the blood of some animal 

 whose blood-cells are almost the same 

 as those of man, then the microscopi- 

 cal evidence would be sufficient to 

 prove the nature of the stain, and to 

 disitnguish the blood-cells from those 

 of birds, etc. But, on the other hand, 



we have grave doubts, which are 

 shared by many microscopists of ex- 

 perience, if the shape and size of the 

 cells of dried blood, obtained from 

 woven fabrics by soaking in mercuric 

 chloride, or in any other way, are 

 sufficiently characteristic to justify any 

 positive evidence of their origin, 

 based upon our present knowledge 

 and experience. 



We do not express the opinion that 

 it is impossible to distinguish the dif- 

 ferent kinds of corpuscles in this way. 

 On the contrary, it seems very proba- 

 ble that it can be done. There seems 

 to be great constancy in the average 

 sizes of the corpuscles of different ani- 

 mals, and, providing a sufficient num- 

 ber of them are measured to get a fair 

 average size, there is no doubt of our 

 ability to distmguish different speci- 

 mens of fresh blood with absolute 

 certainty. But in dealing with dried 

 blood, especially such as is dried 

 upon cloth, or fibrous surfaces, the 

 corpuscles are likely to be distor- 

 ted, and it is more difficult to get 

 a fair average by measurements. 

 Moreover, the shrinkage of corpuscles 

 in drying may be greater or less under 

 different circumstances, and its amount 

 is not yet known with any certainty. In 

 any case it must be very slight, to be 

 sure, but in a matter of such vital 

 importance it cannot be neglected 

 by the scientific observer, until its 

 amount is known for all circumstances. 

 Granting the strong probability that 

 the microscope does, under favorable 

 circumstances, afford a means of posi- 

 tively identifying human blood, and 

 distinguishing it from all other blood, 

 we must still hold to the opinion that, 

 until experience has shown such evi- 

 dence to be sure and infallible, no 

 scientific man is warranted in stating 

 that a stain upon cloth is made by 

 human blood, from the microscopical 

 examination alone. 



Doubtless in the particular case re- 

 ferred to, the microscopist was fully jus- 

 tified in giving the positive testimony 

 that has been reported, but we would 

 particularly impress upon the reader 



