ABSTRACT
The Psorospermia are microscopical corpuscles of a peculiar kind, which may be generally characterized, in the full-grown condition, as rounded organisms, having a sharply-defined outline, with or without a tail-like appendage. They are flattened and lenticular in figure, and one pole is usually acuminute; and towards this pole several internal vesicles converge in a symmetrical manner. These creatures were discovered by Joh. Miiller in 1841 (Mull. Arch., 1841, p. 477). He found in a young Pike minute round cysts in the cellular tissue of the muscles of the eye, in the substance of the sclerotica, and between this and the choroid coat. The contents of the cysts was a whitish substance, which, when examined microscopically, was found to consist of peculiar elements—the “ Psorospermia.” [A detailed notice of these observations is given in the ‘ Microscop. Journal,’ vol. ii. p. 123, and in the ‘ Brit, and Foreign Med. Rev.,’ January, 1842.] In the following year the same observer (Müller’s Arch., 1842, p. 193) discovered parasitic corpuscles in the swimming bladder of a Gadus callarius, which, although specifically distinct from the Psorospermia, approached very near the latter in their organization. They resembled in general a smooth ventricose Navicula, and consisted of two elongated cases applied to each other at the cavity, and with an elliptical outline and convex outer surface. They were in part free, in part enclosed in masses within a tunic. Similar cysts, containing “ Psorospermia,” have been found by Leydig in several species of fish, and in all parts nearly of their bodies, and even in the blood contained in the heart (p. 223), and in the peritoneal cavity.
Some facts, however, observed by him, connected with this subject, which came under his notice in 1850, during some researches on the cartilaginous fishes, served to throw a more general light upon these mysterious forms.
In the gall-bladder of a Squatina angelus, there occurred, in the bile, and in large quantity, peculiar forms of various organization, but which were manifestly developmental forms. I. Rounded vesicles, consisting of a delicate membrane and a consistent fluid. The latter was of a yellow colour and contained a multitude of also yellow granules. 2. Other vesicles presented, besides these, other elements of a new kind. In the middle of the granular contents were several perfectly transparent cellules. Small vesicles had only one of these cellules, larger ones as many as six. 3. Other parent vesicles, again, exhibited, besides their membrane, a granular contents and secondary vesicles, containing Psorospermia, always one in each secondary vesicle. 4. In the latter form, finally, the secondary vesicle had attained a large size, and the Psorosperm floated in a spacious clear chamber, which occupied nearly the whole of the parent cyst. Besides these motionless cysts, there were numerous free Psorospermia in the bile.
He found, upon examination, very similar things in other fishes of the same class,—as in Spinax vulgaris, Scyllium canicila, Torpedo narke, and Raja batis, in which the Psorospermia differed from the more usual form, in their being grooved or ribbed.
It was very remarkable that the above-described organisms were never met with in any other part or tissue of the body than the gall-bladder or biliary duct.
With respect to the nature of these bodies, Leydig is inclined to think that the cyst should be regarded as belonging to the family of the Gregarinae, and that the “ Psorospermia “ must be looked upon as generically analogous to the “ Pseudonavicella?,” which have been observed to be generated within the Gregarinæ.
The question next arises as to the existence of similar Gregariniform organisms producing Psorospermia, in freshwater fishes. Leydig thinks there is reason to suppose that the animalcule discovered by Valentin in the blood of Salmo fario is a Gregarina. Moreover, John Müller and Leydig have observed two or three ecaudate Psorospermia in Leuciscus dobulst, enclosed in a cyst. Whence it might be supposed that secondary cells may be developed within one of Valentin’s Haeinatozoa, after it has been conveyed, in the course of the circulation, to one organ or another; in which cells Psorospermia may originate. With the growth of the latter the granular contents of the Gregarinæ gradually disappear, which are thus transformed into cysts filled with Psorospermia. Such a cyst would then be equivalent to a N a vice! la-receptacle.
The author then proceeds to discuss the vexata quaistio of the true nature of the Gregarinæ; and, adverting to the conflicting views of Kolliker and Bruch, declares himself in favour of the latter, which assumes, as above stated, that the Gregarina is a transformed Filaria, or Anguillula.
In the intestine of a large species of Terebella he was enabled to observe the most distinct transition between Filarialike nematoid worms and Gregarinæ. The forms of the latter which he observed, not once only but many times, were—1. A Gregarina of from 0·02‴ to 0·04‴ long, which had the form of an elongated sac, rounded at one extremity, and sharp at the other. The contents were those usual in the Gregarinæ, a consistent fluid with a corpuscular substance, which did not occupy the pointed end, and imbedded in this a clear vesicle with a nucleus. 2. A Gregariniform creature, of a spindle-shaped figure, closely resembling Gregarina Terebellce, Köll 3. A Gregarina, generally resembling the preceding, differing only in two particulars. The internal substance is arranged in longitudinal streaks, and the body, instead of being straight, is more or less curved at each end. 4. The same form, but with the body more elongated, vermiform; and, for the first time, exhibiting motion. 5. A very pretty nematoid worm, about 0 10”‘ long ; blunt at one end, sharp at the other; the contents in longitudinal streaks, as in the two preceding forms, but with the spaces between them wider. Its motions are very active.
Leydig is induced, by considerations of the above facts, and by other reasons, to believe that the Gregarinae are not perfect animals, but “ a link in the series of development of the Helminthes,” as Henle expresses it. Another question, however, arises: do the Gregarina; become changed into Filariaform worms, or is it that the Filaria-like worms are metamorphosed into Gregarinae ? Although at first inclined to consider the former as the true state of the case, Leydig is now disposed to follow Henle and Bruch, and adopt the latter view; otherwise it would seem impossible to account for the formation of the “ Pseudo navicellae “ and “ Psorospermia “ within the Gregarinae.
