their Secretions, 621 



contractions and dilatations were very strong, a piece of the 

 membrane or layer containing the spots, about two tenths of 

 an inch square ; this I separated completely from the animal, 

 and placed it in a watch-glass immersed in sea-water in an- 

 other vessel. To my astonishment, I saw that the spots in the 

 separated portion continued in as lively motion as when con- 

 nected with the animal. No change, either in the velocity 

 or extent of their motions, could be perceived. Some spots, 

 just on the edges of the separated piece, seemed to have been 

 half cut through by the scissors with which I removed it : 

 such did not contract; but all the others in the piece moved 

 in the very same manner as before. 



" I now removed the watch-glass, containing the separated 

 portion, to the stage of a microscope, and examined the spots 

 with powers of 100 and 150. This, however, gave me no 

 advantage ; I saw nothing more than I had previously ob- 

 served with the naked eye. San Giovanni has compared the 

 appearance of the structure of the spots to that of felt; but I 

 could not satisfy myself that this was the case in those exa- 

 mined, although I passed through the membrane a very strong 

 light. I saw that the spots were very thin bodies, attached 

 to the mucous coat of the integument; that they had no con- 

 nection with the epidermis; that, in dilating, their edges 

 passed over or under each other indiscriminately ; that their 

 edges were extremely sharp and well defined ; that they never 

 were increased in thickness during dilatation ; and that no 

 vessels carrj^ing coloured fluids entered them. I could not 

 discover, indeed, any thing like either vessels or nervous fila- 

 ments connected with any part of the integument of the ani- 

 mal ; and I feel assured, that, from the great size of some of 

 the spots which I had under the microscope, I must have seen 

 at least a few vessels carrying dark-coloured fluids entering 

 the mucous coat, had it been from such a source that the in- 

 crease in size of the spots was derived. 



" The separated piece of the mucous coat, with the palpi- 

 tating spots, remained under my microscope, exposed to a 

 strong reflected light, for three quarters of an hour, during 

 which time I could perceive no alteration in its appearance, 

 or the strange phenomena it presented. While the motions 

 of the spots were very brisk, I suddenly removed it to a dark 

 place, where it remained fifteen minutes. On bringing it again 

 to the light, I found that all motion had ceased ; most of the 

 spots were in a state of contraction ; but, on allowing it to 

 remain for three minutes exposed to a moderately strong 

 light, the dilatations again commenced, and were carried on 

 unceasingly for a very considerable time. I repeated these 



