566 ELEMENTARY PHYSIOLOGY 



VIL Nervous Action. 



A nervous impulse travelm along a nerve at the rate of 

 about 80 feet in a second in the frog, but much more 

 rapidly in man. 



VIII. HiSTOLOGT. 



The following are some of the most important histo- 

 logical measurements : — 



Red blood-corpuscles, breadth jrg'iygth of an inch, or 



7 /I* to 8 ju.. 



White blood-corpuscles, breadth ^s^yjjth of an inch, or 

 ID ^.. 



Striated muscular fibre (very variable), breadth jj^^th of 

 .11 inch, or 60 jn ; length Ih inch, or 30 to 40 millimetres. 



Non-striated muscular fibre (variable), breadth ^-jj'oiT^h 

 of an inch, or 6 /n ; length ^^gth of an inch, or 50 /x. 



Nerve fibre (very variable), breadth ^-^fyijth to aoVfj*^^ 

 of an inch, or 2 /i to 12 fx. 



Nerve cells (of spinal cord) excluding processes, breadth 

 gjfjth to 25T5*^^ o"* r"ore of an inch, 50 fj. to 100 /n or more. 



Fibrils of connective tissue, breadth 2 s^orr^^ ^^ ^^ inch, 

 or 1 n- 



Superficial cells of epidermis, breadth ys's^ff*'^ ^^ ^^ 

 inch, or 25 ju. 



Capillary blood-vessels (variable), with ^^gjjth to ofyViyth 

 of an inch, or 7 m to 12 /n. 



Cilia, from the wind-pipe, length ^qVcj ^^ ^" i"'^^ ^^ 



8 ju.. 



Cones in the yellow spot of the retina, width g(j\jffth of 

 an inch, or 3 jm. 



