BLOOD 39 



of the murdered man's shirt and neckerchief. 7. There . 

 were present also numerous tessellated epithelial cells. In 

 order to understand the meaning and the bearing of this 

 last fact, I must explain that the whole of the internal sur- 

 face of the body is lined with a delicate membrane (a con- 

 tinuation of the external skin), which discharges mucus, 

 and is hence termed mucous membrane. Now this is com- 

 posed of loose cells, which very easily separate, called 

 epithelial cells; they are in fact constantly in process of 

 being detached (in which state they constitute the mucus), 

 and of being replaced from the tissues beneath. Now 

 microscopial anatomists have learned that these epithelial 

 scales or cells, which are so minute as to be undiscernible 

 by the unaided eye, differ in appearance and arrangement 

 in different parts of the body. Thus, those which line the 

 gullet and the lower part of the throat are tessellated, or re- 

 semble the stones of a pavement; those that cover the root 

 of the tongue are arranged in cylinders or tall cones, and are 

 known as columnar; while those that line some of the vis- 

 cera of the abdomen carry little waving hairs (cilia) at 

 their tips, and are known as ciliated epithelium. 



The result of the investigation left no doubt remaining 

 that with that knife the throat of a living human being, 

 which throat had been protected by some cotton fabric, 

 had been cut. The accumulation of evidence was fatal to 

 the prisoner, who without the microscopic testimony might 

 have escaped. 



But what was there in the dried brown stain that de- 

 termined it to be blood? And, particularly, how was 

 it proved not to be the blood of an ox, as the prisoner 

 averred ? To these points we will now give a moment's 

 attention. 



