BLOOD. 25 



CHAPTEK II. 



The microscope is daily becoming a more and more im- 

 portant aid to legal investigation. An illustration of this 

 occurred not long ago, in which a murder was brought 

 home to the criminal by means of this instrument. Much 

 circumstantial evidence had been adduced against him, 

 among which was the fact, that a knife in his possession 

 was smeared with blood, which had dried both on the 

 blade and on the handle. The prisoner strove to turn 

 aside the force of this circumstance by asserting that he 

 had cut some raw beef with the knife, and had omitted to 

 wipe it. 



The knife was submitted to an eminent professor of 

 microscopy, who immediately discovered the following 

 facts :■ — 1. The stain was certainly blood. 2. It was not 

 the blood of a piece of dead flesh, but that of a living body; 

 for it had coagulated where it was found. 3. It was not 

 the blood of an ox, sheep, or hog. 4. It was human 

 blood. Besides these facts, however, other important 

 ones were revealed by the same mode of investigation. 



5. Among the blood were found some vegetable fibres. 



6. These were proved to be cotton fibres, — agreeing with 

 those of the murdered man's shirt and neckerchief. 



7. There were present also numerous tesselated epithelial 

 cells. In order to understand the meaning and the bear- 

 ing of this last fact, I must explain that the whole of the 

 internal surface of the body is lined with a delicate mem- 

 brane (a continuation of the external skin), which dis- 



