12 LABORATORY DIRECTIONS IN 



substance is the matrix. What inference may be made concerning its 

 origin? Draw a few groups of cells, showing the structure of at least two 

 of them, and representing also the matrix. 



56. Bone Cells. Examine prepared sections of dry bone. The 

 dark spots are the spaces or lacunoe (little lakes) formerly occupied by 

 the bone cells. Projecting from the lacunae are minute wavy channels, the 

 canaliculi (little canals) into which in life extend slender processes (like 

 pseudopodia) of the bone cells. Larger openings, for blood vessels, may 

 occur in the preparations. The remainder of the specimen consists of 

 the hard parts, mostly calcium salts, deposited in the matrix. The 

 fleshy parts of the bone are dried and shriveled in these preparations. 

 What is the origin of the matrix? 



Draw carefully a lacuna with its canaliculi as representing the form of 

 a bone cell. 



5c. Remove a hair from your eyebrow, mount it in water and examine 

 at different points along its length both on the margin and on the upper 

 surface. Can you detect anything that would indicate cells? Sketch a 

 segment of the hair to show them. In the sketch the diameter of the hair 

 should be one-half inch. 



5d. Wool is similar to hair in its composition. Examine the minute 

 fibers from a woolen blanket. Are there any indications of cellular 

 structure? 



5e. Human Blood. This exercise is not required. Any one who desires 

 to examine his own blood will be shown how to do so with comparative 

 safety and with the minimum of pain. Mount the blood, and examine the 

 red corpuscles. What is their color when seen singly ? Is there a nucleus ? 

 Examine a demonstration of stained human blood. 



6. Is the Whole Animal Body 1 Made up of Cells? 



6a. Examine a longitudinal section of a small salamander. The names 

 of most of the structures (organs) which you find there maybe determined 

 by consulting the wall chart. Make a list of all the organs which you 

 think are made up of cells? Do you find any organs not made up of cells? 

 If so make a list of them also. If you are in doubt as to the interpretation 

 of any of the observations consult the instructor or the assistant. (The 

 presence of nuclei may be taken as evidence of the existence of cells if 

 the cell outlines cannot be determined.) 



66. Recall also in connection with this problem the parts of the animal 

 body studied la, 16, Ic, 2c, 3a, 4, 5a, 56, 5c, 5d, 5e. 



B. SUMMARY 



In your summary state the general conclusions in regard to the cell 

 which may be derived from the facts presented in this exercise. 



1 To the teacher: By the addition of proper plant material this problem may be 

 made to cover all living things. 



