REARING HELMINTHES FEEDING EXPERIMENTS 115 



CHAPTEE IV. 

 BEARING HELMINTHES FEEDING EXPERIMENTS. 



THE progress which has recently been made in Helminthology is ; 

 to a large extent, the outcome of experiments in hatching and rearing 

 Helminthes. These experiments are undertaken with the object of 

 following the life-history of the worm through its various develop- 

 mental stages. As a general rule, Helminthes do not live in the open, 

 and the only way to develop them is by reproducing the conditions 

 under which they normally thrive. In other words, they must be 

 reared within the body of a suitable host. At a certain stage of their 

 development, the worms, either with or without a vehicular mass, are 

 introduced by the mouth into the body of an animal of a certain 

 species. The different varieties of Helminthes are parasitic in certain 

 definite host-species only and, if introduced into the bodies of other 

 hosts, they fail, as a rule, to develop. To discover the precise host- 

 species in which a certain stage of Helminth will continue its develop- 

 ment is by no means an easy or a simple matter. The beginner will 

 do well to confine himself to experiments, the result of which has 

 been already ascertained. 



The first experiment of the kind was carried out at the end of the 

 eighteenth century by P. C. Abildgaard. The striking similarity 

 between the immature tapeworms so frequently encountered in the 

 body-cavity of the stickleback (Gasterosteus aculea^tus) and the mature 

 forms found in the intestine of water-birds, led him to suspect that the 

 tapeworm of the stickleback attains maturity and deposits eggs, only 

 after it has reached the intestine of the water-bird. At that time, 

 and indeed much later, sexually immature Helminthes were univer- 

 sally regarded as of separate species, and experiment alone could 

 determine whether the suppositions of Abildgaard were justified by 

 facts. To put the matter to the test, two farmyard ducks were for 

 some days fed with sticklebacks. Upon examination, the intestines of 

 these ducks were found to contain worms in the sexually mature 

 form, exactly similar to those found in the bodies of wild ducks, which 

 are known to feed upon sticklebacks. The condition of sexual maturity 

 was undoubtedly brought about by a fe^w days' sojourn within the 

 body of a fresh host of suitable species. 



Although this experiment established a precedent, showing as it 

 did the connection between the mature tapeworm and a young form 

 resembling it, other experiments of the kind were not made. It was 

 not until 1851 that F. Kiichenmeister again made use of the method, 

 and since that date it has proved of the utmost value in practical 

 Helminthology. By means of experiments similar to those of 



