86 



MICROSCOPICAL DIAGNOSIS. 



sionally a star-shaped and central nucleus is present. The large 

 grains average T J T of an inch, the small grains g^T of an inch in 

 diameter. A distinct cross is seen in rye starch with the polarized 

 light. After examining these starches in their natural condition, 

 they should be subjected to both dry and moist heat, and examined, 

 as their appearance is much changed by heating. As adulterants, 

 they are frequently so treated. 



Bean Starch. We have here a very different appearance from 

 any other starch, excepting that of the pea. The grains are regular- 

 ly oval and quite uniform in size. A dark line with ragged edges 



generally extends the whole length of the grain ; cross-marks being 

 frequently seen. Faint rings are seen near the edge of the grain. 

 The grains average about I T of an inch in length and J^Q- of an 

 inch in breadth. Dry heat renders the grains more brittle, and 

 destroys the nucleus, but not the rings. Moist heat expands, dis- 

 torts, renders more transparent, and destroys both rings and nucleus. 



Pea Starch is the nearest like that of bean starch. The grains 

 are smaller and more slender, being generally less than yj-g- of an 

 inch in length. 



Corn Starch. We come now to a starch grain bounded by plane 

 faces and angles instead of curves. The grains are angular, have no 

 rings, and present a round or star-shaped central nucleus. The 

 average grain is y^Vo ^ an mcn m diameter. The shape is only 



