MICROSCOPICAL DIAGNOSIS. 



(page 59), which is too long, however, for an explanation in this con- 

 nection. In specimens which have been subjected to even a slight 

 degree of dry heat, there appears a black line or star-shaped mark 

 over the nucleus. The heat evaporates the moisture from the grain, 

 and there must be a shrinkage on the surface to correspond with the 

 evaporation. This is the greatest over the nucleus where is the 

 greatest moisture. The grains are round, ovate, irregularly oval, or 

 egg-shaped, nearly transparent ; nucleus eccentric and in the 

 smaller end of the grain, and surrounded by numerous 

 distinct rings or laminae. The grains are very irregular in size ; the 



Fig. jo. Potato Starch. XJ75. 



smallest are just perceptible, and the largest are frequently T ^ of an 

 inch in length. A very decided cross is seen when viewed with 

 polarized light, the arms of the cross radiating from the nucleus, not 

 from the centre of the grain. This is the cheapest and the most 

 common starch ; there being from $800,000 to $1,200,000 worth 

 thrown on the market annually. Probably the greatest part is used 

 for adulterations. 



Arrow-root Starch closely resembles potato-starch. The grains 

 are much more uniform in size than those of the potato, and are 

 about -g^fr of an inch in length. The nucleus is generally in the 

 larger end of the grain, while in the potato-starch, as before men- 

 tioned, it is in the smaller end ; while the rings are finer and more 



