578 ORDER HE TERO TRIG HA . 



Balantidium coli, Malmsten sp. PL. XXIX FIGS. 16 AND 17. 



Body shortly oval, almost egg-shaped, subcylindrical, from one and a 

 half times to twice as long as broad, the anterior extremity to a small extent 

 obliquely truncate ; peristome-field very short, median, triangular, curved 

 towards the right ; no distinct pharynx ; endoplast elongate-ovate ; con- 

 tractile vesicles two in number, located medianly and posteriorly towards 

 the right side of the ventral surface. Length 1-360" to 1-168." 



HAB. Rectum of swine and of the human subject. 



Attention was first directed in a notable manner to this animalcule by Professor 

 P. H. Malmsten, of Stockholm, who described it in Virchow's ' Archiv fur Patho- 

 -logische Anatomic' in the year 1857, under the title of Parametium (?) coli. The 

 specimens forming the subject of this description were discovered in profusion 

 within the faecal evacuations of two patients admitted to the Stockholm Hospital, 

 both suffering from chronic diarrhoea, and one of whom succumbed to this disease. 

 A post-mortem investigation showed the surface of the large intestine to be con- 

 siderably ulcerated, and its cavity above the sigmoidal flexure to be filled with a 

 pungent, fetid liquid. A number of these Balantidia were found both in this 

 liquid and in the neighbourhood of the ulcerated portions, but not in such abundance 

 as in connection with the mucus-lining of the more healthy parts of the caecum and 

 vermiform appendage. This circumstance renders it doubtful whether or not these 

 animalcules were the cause, or merely an accompaniment of the disease in question, 

 the subject being at all events well worthy of further investigation. No trace of 

 these Infusoria was detected above the valve of the colon. This endoparasitic 

 species has been since found by Stein in great abundance in the rectum and faecal 

 evacuations of the common hog. 



Balantidium duodeni, Stein. 



Body shortly ovate or broadly almond-shaped, scarcely longer than 

 broad, considerably flattened ; the ventral surface much less convex than 

 the dorsal one, and from which in profile it seems separated by a line or 

 angle of demarcation ; peristome-field narrow, cleft-like, produced on the 

 right side nearly as far as the centre of the lateral line ; no distinct pha- 

 ryngeal prolongation ; endoplast ovate ; contractile vesicle single, situated 

 towards the right-hand side of the posterior extremity. Length 1-288" to 

 1-192". HAB. The duodenum of the edible frog, Rana esculenta. 



This species, while found enjoying the hospitality of the same amphibian as 

 Balantidium entozoon, is reported by Stein to be entirely confined to the mid-intestine 

 or duodenum of that host, which position it monopolizes to the exclusion of all 

 other infusorial forms. The general surface ciliation of this animalcule is highly 

 characteristic, being longer and finer than in the species previously described, 

 mostly directed forwards, and having a tendency to group itself, as with Conchophthirus 

 and many Opalinidse, into even, longitudinally disposed, pencil-like tufts. Multipli- 

 cation by transverse fission has been frequently observed. 



Balantidium medusarum, Mereschk. PL. XXXII. FIG. 22 



Body soft and flexible, variable in form, more or less ovate or sub- 

 cylindrical, almost two and a half times as long as broad, the posterior 

 extremity rounded, the anterior one from left to right obliquely truncate ; 

 peristome-field produced backwards in the median line to the centre of the 



