BLOOD TISSUE 



87 



Slenolrite^ 



the dendrites, nerve cells connect with each other. The axon 

 is the process which connects the nerve cell with a structure 

 remote from the cell body. 



If one hears a sound and walks toward 

 it, an axon has carried the sound from 

 the ear to a nerve cell in the brain. By 

 means of dendrites, a connection was set 

 up with another nerve cell which in turn 

 carried the message to muscle cells. The 

 muscle cells contracted so as to make 

 walking possible. Axons vary in length : 

 some are microscopic while others may be 

 as long as two or three feet. The cell 

 body is always of microscopic dimensions. 

 Nerve cells attain the highest development 

 of irritability. They are the highly sensi- 

 tive cells of the body. They receive mes- 

 sages, transmit them, and regulate _ the tt~!m?jSff5i 

 responses to these messages. Nerve tissue has s . everal processes, one 



a F sometimes very long, the axon. 



will be studied in greater detail in a later Although the ceil body, cyton, 



is microscopic, the axon, also 



chapter. microscopic in diameter, may 



, .. . . -r,, , . .... n ., be two or three feet long. 



Blood tissue. Blood is so highly fluid 



that it is not usually considered a tissue. A tissue has been 

 defined as a group of similar cells, and blood, consequently, may 

 be considered a tissue since it consists of groups of similar cells. 



Problem. Study of blood tissue. 



Press the finger near the tip until blood congests. Prick the end of the finger 

 with a needle that has been passed through a flame to sterilize it. Touch a 

 cover glass to the drop of blood on the finger ; invert the cover slip on a glass 

 slide. Mount under the low, then under the high power of the microscope. 



I. Describe the shape, size, and color of the more numerous cells seen. 

 These are the red corpuscles. 



II. Examine all the substance under the microscope carefully and find 

 an occasional irregularly shaped cell. This is a white or amoeboid corpuscle. 



- terminal brandies. 



