342 THE MICROSCOPE. 



granule as a perfect cell, from the phenomena presented 

 during its decay or dissolution, when left for some time in 

 water. Sehleiden and others, after examining its expan- 

 sion and alteration under the influence of heat and of 

 sulphuric acid^ considered it to be a solid homogeneous 

 structure. 



Professor Busk agrees with M. Martin in believing the 

 primary form of the starch-granule to be " a spherical or 

 ovate vesicle, the appearance of which under the micro- 

 scope, when submitted to the action of strong sulphuric 

 acid, conveys the idea of an unfolding of plaits or rugse, 

 which have, as it were, been tucked in towards the centre 

 of the starch-grain." 1 The mode of applying the concen- 

 trated sulphuric acid is thus described by Mr. Busk : — " A 

 small quantity of the starch to be examined is placed 

 upon a slip of glass, and covered with live or six drops of 

 water, in which it is well stirred about ; then with the 

 point of a slender glass-rod the smallest possible quantity 

 of solution of iodine is applied, which requires to be 

 quickly and well mixed with the starch and water; as 

 much of the latter as will must be allowed to drain off, 

 leaving the moistened starch behind, or a portion of it 

 may be removed by an inclination of the glass, before it is 

 covered with a piece of thin glass. The object must be 

 placed on the held of the microscope, and the 5-inch 

 object-glass brought to a focus close to the upper edge of 

 the thin glass. With a slender glass-rod a small drop of 

 strong sulphuric acid must be carefully placed immediately 

 upon, or rather above the edge of the cover, great care 

 being necessary to prevent its running over. The acid 

 quickly insinuates itself between the glasses, and its course 

 may be traced by the rapid change in the appearance of 

 the starch-granules as it comes in contact with them. 

 The course of the acid is to be followed by moving the 

 object gently upwards ; and when, from its diffusion, the 

 re-agent begins to act slowly, the peculiar changes in the 

 starch- granules can be more readily witnessed. In pressing 

 or moving the glasses, the starch disc becomes torn, and 

 is then distinctly seen, especially in those coloured blue, to 



(I) Professor G. Busk, F.R.S.. on tjie Structure of the Starch-granule ; Quar- 

 teriy Journal of Microscopical Science, April, 1853. 



