HISTORY AND OCCURRENCE. 255 



peristome, which usually extends to the right of the middle line, in the 

 form of a funnel, narrowing to a small cleft, and leading into a short 

 gullet. While feeding the peristome is tooadened out, so as to look like a 

 triangular surface, sloping away obliquely towards the anterior loi^der. 



FIG. 127. Balantidium coli, with widely FIG. 128. Paramcecium (?) coli. 



opened peristome (dorsal view). (After Malmsten). 



The nucleus is elliptical, and slightly lent, two sluggish contractile 

 vacuoles usually lie on the right side, one behind, the other further for- 

 ward. The anus is hardly perceptible. 



Balantidium coli (Fig. 127) was first detected in 1856 by Professor 

 Malmsten, in Stockholm, in the stools of a man who had two years 

 before suffered from a violent attack of cholera, and had since continu- 

 ally complained of dyspepsia, and was alternately affected with consti- 

 pation and with painful diarrhoea. On examination of the rectum there 

 was seen, about an inch above the anus, a small sore, which produced 

 a purulent secretion, mixed with blood ; in this the Infusoria were 

 found in large numbers. Even after the wound healed the former 

 troubles remained, and the Infusoria were still found in the faeces 

 and intestinal mucus. Even at the time of discharge the almost 

 convalescent patient was still infested with the parasites, although 

 their number had considerably decreased. The investigation of the 

 Infusorian was undertaken with the help of the famous zoologist 

 Loven, and it was he who recognised it as new, and referred it 

 (Fig. 128) with some hesitation to Ehrenberg's holotrichous genus 

 Paramcecium. Soon afterwards the parasites were abundantly ob- 

 served in a woman who had suffered for years from a severe in- 

 testinal trouble, and who applied for treatment enfeebled by continual 

 diarrhoea, with bloody and purulent stools. The patient died after a 

 short time. During the last stages of the disease the faeces had been 

 voided involuntarily, and with a fearful stench. Post mortem examina- 

 tion showed numerous small gangrenous ulcers in the large intestine, 



