1883.] on the Swelling of Starch Grains. 403 



violet red tint. In such cases the swelling of the grains, and form- 

 ation of laminated fovilla, proceeds too slowly to allow one to 

 observe anything but the ultimate effects ; but sometimes grains 

 can be noticed of which the swelling is more active. Such a case 

 is figured, at short intervals, in Figs. 4 — 7. The grain can be seen 

 to have almost imperceptibly exfoliated, as it were, layer after layer 

 from a gradually diminishing solid remnant, which preserves in 

 general a position in the mass of fovilla analogous to that of the 

 nucleus in the normal grain. Usually, though not very markedly 

 in the examples figured, the lamination is much more pronounced, 

 and the laminae apparently more numerous, in the direction of the 

 longest radius of the grain, that is, the side on which the normal 

 lamellae are best developed. Externally each lamina is distinctly 

 limited, while in optical section it often shows its two limits by a 

 double line. The smaller and rounder grains usually show the 

 process first. 



After twenty-four to forty-eight hours the whole of the grains 

 in a preparation are swollen, the whole mass of fovilla correspond- 

 ing with each grain laminated, and more or less corrugated. In 

 cases where the solid remnant of the grain has not entirely disap- 

 peared the outer portion of this frequently shows signs of swelling 

 similar, but on a more delicate scale, to that described in methods 

 3 and 4. The mass of fovilla has taken a purplish-red tint. 



The length of time during which the laminated swollen grains 

 retain these appearances, while still remaining surrounded by the 

 reagent, varies considerably, sometimes extending to 4 or 6 weeks. 

 Ultimately they are entirely dissolved, forming a mass of colourless 

 fluid fovilla, if such a term can be applicable. 



Now what is the bearing of these phenomena on our knowledge 

 of the physical and anatomical constitution of the starch grain ? 

 Let us premise that variability in the action of the reagent is of no 

 special importance, beyond telling tis, what every physiologist 

 knows already, that very slight variations in the conditions may 

 induce considerable differences in the results. If we assume that 

 starch grains are formed in any one way, we have equally to face 

 variable appearances in the mature grains, as well as varying 

 responses to the action of reagents. In order then to answer the 

 above question we will first eliminate the phenomena which give 

 us no positive information. Thus swelling by method 1 tells us 

 nothing but what, having regard to variations in conditions, may be 

 referred to method 2. In this case (2) the grain ruptures. This 

 implies that the outer layer of the starch grain is resistant. On 

 rupture the free edges curl outwardly, — the expression of the ten- 

 sion to which the layer is subjected, and by which its rupture is 

 brought about. Further than this the case gives us nothing but 

 negative results. 



