1894.] MICROSCOPICAL JOURNAL. 103 



conclusions that can be drawn, to which there are no lim- 

 itations. As regards the measurement of blood corpus- 

 cles, no one will dogmatically assert that human cor- 

 puscles can never be mistaken for those of any other 

 animal. But even if there must be some reservation 

 made in this general conclusion, the statement is still a 

 scientific one, irrespective of its universality. More than 

 that it is of value in the trial of a case where the origin 

 of a given specimen of blood is involved, if it can be 

 shown that the exceptions to the general rule are few or 

 unusual. All authorities agree that the average size of 

 a dog's blood is smaller than that of a man, but it is not 

 possible to say with mathematical certainty that a given 

 specimen of blood is human. Suppose that an observer 

 could determine, in all but one case in a thousand, 

 whether blood was that of a man or dog, would it not be 

 valuable evidence ? Certainly, there is very little testi- 

 mony ever given in a court of as high character as this, 

 and the same principle applies if the observer could only 

 determine ninety cases in a hundred, the percentage 

 merely being different. The difficulty with the law in 

 the use of scientific evidence is that it demands more 

 than science can possibly give. It asks that all conclu- 

 sions should be without exception, and yet there is 

 scarcely a general proposition in all the range of med- 

 ical science, except perhaps in anatomy and surgery, 

 which can be stated without limitation. Yet, in my 

 judgment, the determination of human blood, as against 

 all other animals except perhaps a dog, can be made with 

 such a degree of certainty, as to entitle the evidence of a 

 well qualified expert on- that subject, to much weight. 

 The narrow rule that the conclusion can at most be, that 

 the blood corpuscles in a given case are consistent with 

 those of human blood, does not, it seems to me, finely 

 state the case. The expert must of course state the lim- 

 itations or exceptions, but he should also be allowed with 



