38 EVENINGS AT THE MICROSCOPE 



these fishes agree in general form with those of the Gold- 

 fish; and also in size, with the exception of trifling vari- 

 ations in the comparative length and breadth. The col- 

 oring matter is lodged in lengthened cylindrical cells, 

 arranged side by side, and running across the scale; that 

 is, in a direction at right angles to the lateral line. 



CHAPTER II 



BLOOD 



THE microscope is daily becoming a more and more 

 important aid to legal investigation. An illustra- 

 tion of this occurred not long ago, in which a mur- 

 der was brought home to the criminal by means of this 

 instrument. Much circumstantial evidence had been ad- 

 duced 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 



