



cells. As they grow older the cytoblast diminishes, and the contents, 

 which at first were clear and gelatinous, become less transparent from 

 containing thousands of granules, which are too small to allow of the 

 passage of light, and consequently appear as dark points ; these atoms 

 are about the 6g £ 00 part of an inch in diameter, and have the motion 

 known as " active molecules." If the vessel be wounded at this pe- 

 riod the gelatinous contents pour slowly out, and then the singular 

 movements of these molecules are still more clearly seen. These 

 atoms, from their freedom of motion, are arranged indiscriminately in 

 the interior of the vessel, but in a short time some of them enlarge, and 

 then transmit a little light, which, on account of their minute dimen- 

 sions, is not suffered to pass as a white pencil, but is decomposed in 

 its course, the granule thereby becoming of a greenish hue. The 

 granules exhibiting this greenish hue are now in a fit state to enter 

 into the composition of the fibre that is to exist in the interior of the 

 membranous tube, and in a spiral vessel this is the manner in which 

 this act is accomplished. 



The granules which are in active motion in the viscid fluid near one 

 of the ends become severally attracted to the inner wall of the vessel, 

 beginning at the very point ; those granules first attracted appear as 

 if cemented to the spot, by the viscid fluid in that direction losing 

 some of its watery character, for there appears a string of a whitish 

 colour, besides granules, in the line which the fibre is to occupy. As 

 the other granules are attracted to those already fixed in an inclined 

 direction, the spiral course is soon to be seen, and the same action 

 progressively goes on, from the end it began towards the other, 

 around the interior of the tube, in the form of a spiral ; the fibre being 

 produced, like a root, by having the new matter added continually to 

 the growing point, thereby causing its gradual elongation. 



This action is not throughout the vessel at the same instant, for I 

 have witnessed a vessel having one half laid down with fibre, and in 

 the other part the operation had not been commenced. When the 

 granules have arranged themselves throughout the whole length of the 

 tube, those which were first deposited, and had then some slightly vi- 

 sible space between them, have by this time been reinforced by others 

 or nourished by the contents of the vessel, so that that space is obli- 

 terated, the fibre beginning to assume a threadlike shape with defined 

 borders, and sufficiently large to allow of the transmission of white 

 light. When this same action has progressed throughout the entire 

 vessel, the transparency begins to be restored, and what is singular, 

 the entire mass of granules has completely disappeared, appearing as 



