438 M. R. Leuckart on Paramecium ? coli, Malmsten. 



At the posterior extremity, a little towards the ventral side, lies 

 the anus, which sometimes projects a little, is sometimes drawn in, 

 and sometimes forms a passage, furnished with several windings, 

 through the cortical layer. The contour of the nucleus is very 

 faintly marked; it is of an elongate elliptical form, with now 

 and then a median constriction, as if from the commencement 

 of division. Two contractile vesicles are present. The larger 

 one is situated quite posteriorly, close to the anal orifice; the 

 smaller one about the middle of the dorsal side. The vesicles 

 contract very slowly, and change their form considerably. In 

 some individuals they were sought for in vain. Besides these 

 parts, the animals showed in their interior a greater or less 

 number of swallowed nutritive matters, generally more or less 

 digested starch-granules and fat-drops." 



The preceding is all that we have hitherto known about this 

 parasitic Infusory ; and I am therefore the better pleased that I can 

 here communicate something new upon it. Not that I have been 

 so fortunate as to observe a fresh case of its occurrence in man. 

 Malmsten's cases still stand alone. But I have found exactly 

 the same Infusory in the colon and caecum of a domestic animal, 

 and indeed so constantly and in such quantities as even to throw 

 some light upon the possibility of its occasional transfer to man. 

 The animal which harbours our Infusory is the pig. In order 

 to observe it, all that is necessary is to draw forth, by means of 

 a long sound, a little dung and intestinal mucus from the rectum 

 and spread it under the microscope. Even with the simple lens 

 the colourless animalcules may then be seen moving through 

 the dung. 



What I have established by my observations on these para- 

 sites of the pig is essentially confirmatory of the statements of 

 Loven and Malmsten. I have to contradict them only on one 

 point ; and this regards the formation of the mouth. For a long 

 time I believed, with the Swedish observers, that our parasite 

 has a lateral mouth, because during the ordinary swimming 

 movements it is usually seen to lie to the right or left near the 

 median line (fig. 12). But this circumstance can prove nothing, 

 because the generally oval body in swimming (both forwards and 

 backwards) continually revolves upon its axis, and consequently 

 presents a median position of the mouth only during the short 

 period of its passage through the median plane. Matters take 

 a very different appearance, however, when we see the animal 

 feed (fig. 13). When this business is going on it applies itself 

 to the nutritive matter with the gaping buccal orifice down- 

 wards, and also creeps for some distance forwards with the mar- 

 gins of the buccal orifice, without any change in the position of 

 the body. The two sides of the body then appear perfectly 



