IRIS. 



667 



part. In a small minority of the grains, in which the 2 

 refractive fissures already described are observed, the 

 hilum enlarges somewhat and the 2 fissures enlarge, and, 

 as they extend more nearly to the distal margin, branch 

 out considerably. The part of the grain included between 

 them and the hilum and the distal margin becomes more 

 refractive in appearance and is divided into fine granules 

 which are placed in rows, retaining the lamellar arrange- 

 ment. Gelatinization occurs first in this part of the 

 grain and proceeds from the hilum towards the distal 

 margin. The more resistant starch at the proximal 

 end and sides nearby forms a lamellated, striated band 

 at the margin, which grows progressively thinner and 

 more nearly transparent, losing at the same time the 

 striated appearance, but retaining the lamellar arrange- 

 ment until the starch is nearly all gelatinized. 



The gelatinized grains are swollen, have rather thick 

 capsules, and are slightly to considerably distorted, but 

 they usually retain some resemblance to the form of the 

 untreated grain. 



The reaction with sodium sulphide begins imme- 

 diately. Complete gelatinization occurs in about 27 per 

 cent of the entire number of grains and 67 per cent of 

 the total starch in 5 minutes; in about 67 per cent of 

 the grains and 95 per cent of the total starch in 15 

 minutes ; in about 87 per cent of the grains and 98 per 

 cent of the total starch in 30 minutes ; little if any further 

 advance in 45 and 60 minutes, respectively. (Chart 

 D453.) 



The reaction with sodium salicylate begins imme- 

 idately. Complete gelatinization occurs in about 19 per 

 cent of the entire number of grains and 27 per cent of 

 the total starch in 5 minutes ; in about 31 per cent of the 

 grains and 50 per cent of the total starch in 10 minutes ; 

 in about 67 per cent of the grains and 75 per cent of the 

 total starch in 15 minutes; in about 98 per cent of the 

 grains and 99 per cent of the total starch in 30 minutes. 

 (Chart D 454.) 



The hilum is distinct, and a small bubble is often 

 formed there. The lamellae gradually become moderately 

 distinct, and remain so until obliterated by gelatinization. 

 The grains become more refractive in appearance, after 

 the reagent is added, and the first part of the grain to 

 show this is the margin, about which a rather narrow, 

 refractive band is formed. Gelatinization begins at the 

 distal margin at a number of discrete points, which are 

 first invaded by short, wide cracks extending inward 

 only to the limits of the refractive marginal band already 

 mentioned. The starch on either side of these cracks is 

 then gelatinized, and rounded hollows are formed, which 

 persist for some time. In the meantime the marginal 

 material between these points is gelatinized, and gela- 

 tinization proceeds toward the hilum and proximal end. 

 Gelatiuization proceeds smoothly, the hollows first formed 

 being obliterated in most of the grains, and the reaction 

 is often preceded by the invasion of the ungelatinized 

 grain, by indistinct, faintly refractive fissures. Just before 

 the hilum is reached, the bubble suddenly enlarges, and 

 then is seen to extend down a canal which is formed 

 in the interior of the grain from the hilum to the gela- 

 tanized portion, and then to shrink and disappear, and 

 the hilum enlarges rapidly, leaving only the proximal 

 portion ungelatinized This starch may gelatinize rap- 

 idly or somewhat slowly, and its gelatinization is accom- 



panied by a considerable invagination of the capsule at 

 this point. The gelatinized grains are considerably swol- 

 len, have rather thin capsules, and are very much 

 distorted, retaining little or none of the form of the 

 untreated grain. 



The reaction with calcium nitrate begins immediately. 

 Complete gelatinization occurs in about 7 per cent of the 

 entire number of grains and 32 per cent of the total 

 starch in 5 minutes; in about 45 per cent of the grains 

 and 82 per cent of the total starch in 15 minutes; in 

 about 61 per cent of the grains and 89 per cent of the 

 total starch in 30 minutes; in about 71 per cent of the 

 grains and 95 per cent of the total starch in 45 minutes ; 

 in about 85 per cent of the grains and 96 per cent of 

 the total starch in 60 minutes. (Chart D 455.) 



The reaction with uranium nitrate begins imme- 

 diately. Complete gelatinization occurs in about 3 per 

 cent of the entire number of grains and 16 per cent of the 

 total starch in 5 minutes; in about 23 per cent of the 

 grains and 66 per cent of the total starch in 15 min- 

 utes ; in about 43 per cent of the grains and 84 per cent 

 of the total starch in 30 minutes; in about 60 per cent 

 of the grains and 95 per cent of the total starch in 

 45 minutes ; in about 73 per cent of the grains and 97 per 

 cent of the total starch in 60 minutes. (Chart D 456.) 



The reaction with strontium nitrate begins imme- 

 diately. Complete gelatinization occurs in about 9 per 

 cent of the entire number of grains and 24 per cent of 

 the total starch in 5 minutes; in about 66 per cent of the 

 grains and 89 per cent of the total starch in 15 minutes; 

 in about 86 per cent of the grains and 98 per cent of the 

 total starch in 30 minutes. (Chart D 457.) 



The reaction with cobalt nitrate begins in 30 seconds. 

 Complete gelatinization occurs in about 3 per cent of 

 the entire number of grains and 4 per cent of the total 

 starch in 5 minutes; in about 7 per cent of the grains 

 and 25 per cent of the total starch in 15 minutes; in 

 about 8 per cent of the grains and 36 per cent of the 

 total starch in 30 minutes; in about 14 per cent of the 

 grains and 43 per cent of the total starch in 45 minutes ; 

 in about the same percentage of the grains and 44 per 

 cent of the total starch in 60 minutes. (Chart D 458.) 



The reaction with copper nitrate begins immediately. 

 Complete gelatinization occurs in about 9 per cent of the 

 entire number of grains and 54 per cent of the total 

 starch in 5 minutes; in about 52 per cent of the grains 

 and 82 per cent of the total starch in 15 minutes; in 

 about 73 per cent of the grains and 95 per cent of the 

 total starch in 30 minutes; in about 78 per cent of the 

 grains and 97 per cent of the total starch in 45 minutes; 

 in about 82 per cent of the grains and 98 per cent of the 

 total starch in 60 minutes. (Chart D 459.) 



The reaction with cupric chloride begins immediately. 

 Complete gelatinization occurs in about 11 per cent of 

 the entire number of grains and 38 per cent of the 

 total starch in 5 minutes; in about 58 per cent of the 

 grains and 80 per cent of the total starch in 15 minutes ; 

 in about 79 per cent of the grains and 95 per cent of the 

 total starch in 30 minutes; in about 90 per cent of the 

 grains and 98 per cent of the total starch in 45 minutes. 

 (Chart D 460.) 



The reaction with barium chloride begins imme- 

 diately. Complete gelatinization occurs in about 3 per 

 cent of the entire number of grains and 8 per cant of 



