4-20 



THE ANIMAL PARASITES OF MAN 



to the posterior part of the body. The ova are barrel-shaped and 

 have a thick brownish shell which is perforated at the poles. Each 

 opening is closed by a light-coloured plug. The eggs measure 

 50 //, to 54 p in length and 23 p in breadth ; they are deposited 

 before segmentation. Trichuris trichiura usually lives in the caecum 

 of man, and is also occasionally found in the vermiform appendix 

 and in the colon, exceptionally also in the small intestine ; usually 

 only a few specimens are present, and these do not cause any parti- 

 cular disturbance, although, as Askanazy found, they feed on blood ; 

 in other cases cerebral symptoms of more or less severity are observed 

 when Trichocephali are present in large numbers. At posi-mortems 

 performed soon after death the filiform anterior extremity of the worm 



is frequently found embedded in the 

 mucous membrane (Askanazy). 



The whip worm is one of the most common 

 parasites of man and appears to be distributed 

 over the entire surface of the globe ; it is, how- 

 ever, more frequent in the warmer regions. It 

 is found in persons of both sexes and all ages 

 with the exception of infants. In autopsies it 

 is found in the following numbers : In Dresden 

 in 2*5 per cent., in Erlangen in n*i per cent., 

 in Kiel in 31 '8 per cent., in Munich in 9-3 per 

 cent., in Petrograd in o'i8 per cent., in 

 Gottingen in 46*1 per cent., in Basle in 237 per 

 cent., in Greenwich in 68 per cent., in Dublin 

 in 89 per cent., in Paris in about 50 per cent., 

 and in Southern Italy in almost 100 per cent. 

 On examining the fasces the eggs of the whip 

 worm were found as follows : In Munich in 8*26 

 per cent, in Kiel in 45-2 per cent, in Greifswald 

 in 45 per cent., in North Holland in 7 per cent., 

 in Novgorod in 26-4 per cent., in Petrograd 

 in 5 per cent., in Moscow in 5*3 per cent. 



FIG. 301. Trichuris trichiura : on 

 the left, male ; on the right, female with 

 the anterior extremity embedded in the 

 mucous membrane of the intestine ; 

 below, egg. 



The development of the eggs is completed in water or in moist 

 soil, and occupies a longer or shorter time according to the season ; 

 the eggs possess great powers of resistance, as do the larvae, which, 

 according to Davaine, may remain as long as five years in the egg- 

 shell without losing their vitality. Leuckart proved by experiment 

 that direct infection with Trichuris ovis (Ovis aries) and T. creuata 

 (Sus scrofa dom.) was produced by embryo-containing eggs ; Railliet 

 obtained the same results with T. depressiuscula of dogs, and Grassi 

 subsequently, by means of two experiments, demonstrated the direct 

 development of Trichuris trichiura. In one case embryo-containing 

 eggs were swallowed on June 27, 1884, and on July 24 the ova of 

 Trichocephali were found in the fasces for the first time. 



