XXXU INTRODUCTION. 



same time the exterior membrane of the joint is observed 

 to swell in one point, till it there forms a little mamilla, 

 which is to become the point from which the moving gra- 

 nules finally issue. By the extension of the membrane for 

 the forn)ation of the mamilla, the tender fibres of which it 

 is composed separating, cause an opening at the end of the 

 mamilla, and it is by this passage that the granules escape. 

 At first they issue in a body, but soon those which remain, 

 swimming in a much larger space, have much more diffi- 

 culty in escaping, and it is only after innumerable knockings 

 (titubations) against the walls of their prison, that they 

 succeed in finding an exit. From the first instant of the 

 motion one observes that the granules or sporules are fur- 

 nished with a little beak, a kind of anterior process, always 

 distinguishable from the body of the sporule by its paler 

 colour. It is on the vibrations of this beak that the motion, 

 as I conceive, depends ; at least I have never been able to 

 discover any cilia. However, I will not venture to deny 

 the existence of these, for with a very high power of a com- 

 pound microscope one sees the granules surrounded with 

 a hyaline border, as we find among the ciliated Infusoria 

 on applying a glass of insufficient power. The sporules, 

 during their motion, always present this heak in front of 

 their body, as if it served to show them the way ; but when 

 they cease to move, by bending it back along the side of 

 their body, they resume the spherical form, so that before 

 and after the motion one sees no trace of this beak. The 

 motion of the sporules before their exit from the joint con- 

 sists principally in quick dartings along the walls of the 

 articulation, knocking themselves against them by innu- 

 merable shocks ; and in some cases we are almost forced 

 to believe that it is by this motion of the sporules that the 

 mamilla is formed. Escaped from their prison they con- 

 tinue their motion for one or two hours, and, retiring always 



