Researches into the structure and development of a newly discovered parasitic animalcule of the human skin, the entozoon folliculorum / by Erasmus Wilson.

  • Wilson, Erasmus, Sir, 1809-1884.
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: Researches into the structure and development of a newly discovered parasitic animalcule of the human skin, the entozoon folliculorum / by Erasmus Wilson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the latter bodies (transition ova) varied between —6tpr of an inch in the short diameter, and and in the long axis. The perfect ova are oval in shape, somewhat larger at one end than at the other, about twice the length of their breadth, semitransparent, amber coloured, and composed of nucleated granules or cells inclosed in a thin and yielding membrane. They vary in length from 3-^ to and in breadth from ygy to 3^ of an inch. The first developmental change observable in the ovum is the disintegration of the tesselated plane of nucleated cells which constitute the surface of the ovum, and lie in contact with its investing membrane. These cells, which are at first polygonal in form, become rounded and larger in size, and the cells of the centre of the ovum acquire a considerable preponderance in bulk over those of the periphery. Subse- quently to these changes the cells assume a special arrangement, they become aggre- gated into a small oblong mass, which is curved at each end, and is not unlike the embryo of higher animals, while a space is formed between the trunk of the little mass and the membrane of the egg. The next stage would seem to be the rupture of the egg-membrane and the expulsion of the embryo, but this process I have not observed in operation, although I have seen on the one hand embryos which ap- peared to be just released from their investing membrane, while on the other I have detected egg-membranes evidently cast off by ecdysis. In some few of the ova I have observed adipose cells, some large and some small, mingled with the germinal cells. It is a curious fact, that in the development of the Entozoon folUculorum. a re- markable embryonic form is met with which is peculiar to the long variety of the animal, and is not met with in the shorter kind. This embryonic body is elongated, rounded and bulky at one extremity; smaller, somewhat tapering and blunt-pointed at the other, and enlarged towards the middle by the development from one of its sides of two oval-shaped prominences which subside gradually into the larger end and join the smaller end, either at a right or at a receding angle. This peculiarity of form enables us to divide the embryo into a body, which comprises the larger end and these two oval prominences, and a tail, which is the smaller and shorter end ; the principal changes in its form taking place, in the course of development, being the elongation of the tail and the enlargement or subsidence of the oval prominences. The dimensions of the embryo are 3^ to of an inch in the long, and to 3^ in the short diameter. In structure the embryo presents a close analogy with the ovum, being composed of nucleated cells, having the same disposition and appear- ance, and enclosing in the centre of their mass a number of larger cells. The larger cells correspond in position with the broadest part of the embryo, and extend more or less in proportion to its development into the cephalic and caudal portions. They also vary in their size, the central cells being the largest, while those which surround them are small and more numerous. The smallest of the ova that I have examined are something less in length than