30 LABORATORY MANUAL FOR ELEMENTARY ZOOLOGY 



single cell, and will become separated from each other by the deposit of matrix 

 between them. Draw a small portion of cartilage. 



c) Bone: Examine prepared slide "Frog bone." These slides are prepared 

 by grinding down slices of dried bone; hence the bone cells and other living 

 structures of the bone have been destroyed. In bone, the matrix has been 

 rendered very firm and strong by the deposit in it of mineral salts, chiefly cal- 

 cium phosphate and calcium carbonate, through the activity of the bone cells. 

 This matrix is arranged in concentric layers, called lamellae, around circular 

 holes, which are the cross-sections of canals, the Haversian canals. The Haver- 

 sian canals traverse the bone in a longitudinal direction and in life carry blood 

 vessels, lymph vessels, and nerves for the nutrition of the bone. Scattered 

 through the lamellae are minute spaces, or lacunae, with spidery processes extend- 

 ing out into the matrix. In these spaces the bone cells and their processes are 

 contained in the living condition. Draw a portion of bone. 



4. Blood.- Blood may be regarded as tissue in which the intercellular sub- 

 stance is liquid. The cells of blood are called corpuscles, and the fluid inter- 

 cellular portion, the plasma. The corpuscles are of two general classes, red 

 corpuscles, which give the red color to the blood and carry oxygen, and white 

 corpuscles, which protect the body from disease (Holmes, pp. 258-64). 



a] Fresh blood: Obtain from the assistant a drop of fresh frog blood, stir it 

 up in salt solution, cover and examine with the high power. The numerous 

 oval bodies are the red blood corpuscles, although they are not red except in 

 masses. Scattered here and there among the red corpuscles will be found the 

 white corpuscles, smaller, irregular in shape, and with granular cytoplasm. If 

 you watch a white corpuscle for some time you may see it undergo slow changes 

 of shape, an example of amoeboid movement. By gently moving the cover glass, 

 cause the red corpuscles to float about on the slide, and as they turn determine 

 their shape in profile. The central bulge is due to the nucleus, which is generally 

 faintly visible. 



b) Stained blood: Examine with the high power the slide of blood. Note: 



(1) The red blood corpuscles, the very numerous oval bodies on the slide. 

 Each has a central nucleus. Draw one. 



(2) The white blood corpuscles: As these are much less numerous than the 

 red corpuscles, it will be necessary to search the slide carefully for them. There 

 are several kinds of white corpuscles. Those with a complex nucleus, consisting 

 of several pieces, and with granular cytoplasm are called leucocytes; those with 

 an ordinary type of nucleus and with clear cytoplasm are lymphocytes. Try to 

 identify the following kinds and make drawings of those which you are able to 

 find: 



(a) Polymorphonuclear leucocytes: This type of white blood cell is distin- 

 guished by its very irregular nucleus, which consists of several masses, apparently 

 separate but really united by delicate strands. The cytoplasm is always packed 



