59 



ground shells are white or pearly in color, sand, under the micro- 

 scope varies from white through various shades of pink, red, 

 bro^^^l and yellow. The edges of the particles are not usually 

 so sharph^ defined as in the case of clam or oyster shells. If there 

 is any doubt as to whether the substance under examination is 

 sand or shells a drop of hydrochloric acid may be introduced on 

 the slide and in the case of sand, no effervescence takes place, 

 such as occurs when ground shells are treated with this reagent. 

 The particles of sand are also as a rule much smaller than those of 

 shells. 



CLAM SHELLS, OYSTER SHELLS. 



Ground clam and oyster shells are very often found in chick 

 feeds as well as in other commercial feeds. The particles are large 

 enough to be seen with the naked eye and are white or pearly in 

 color with a decided lustre. Under the microscope they may 

 be distinguished from ground fragments of bone by the absence 

 of the characteristic bone structure, and show no lacunae or any 

 canaliculi. They also give off carbon dioxid more abundantly 

 than do the fragments of bone when a drop of hydrochloric acid 

 is introduced under the cover glass. 



BONE MEAL. 



Fragments of bone meal may be recognized by the characteris- 





Figure 51 

 Fig. 51. Bone meal. Showing lacumae and canaliculi. 



