504 THE ANIMAL PARASITES OF MAN 



called forth by the animal parasites, especially by the entozoa. Formerly, when 

 certain morbid phenomena could not be explained, enigmatical symptoms were 

 ascribed to the accidental presence of one or several parasites, thus -giving rise 

 to many vague conceptions; later there was an evident inclination to ascribe 

 little, or no, reaction upon the affected organism to animal parasites, espe- 

 cially to the entozoa. Undoubtedly, both tendencies were wrong. The phe- 

 nomena observed in many persons infected by parasites, especially the nervous 

 manifestations, cephalalgia, pruritus, disturbances of sight and hearing, 

 mydriasis, sensations of general weakness and lassitude, should not always be 

 regarded as the consequence of helminthiasis. The decision regarding the 

 causal connection depends also upon whether the symptoms have occurred only 

 after the appearance of the parasite and have ceased soon after the expulsion 

 of the unwelcome visitor. Thus, Cobbold and Davaine report a number of 

 cases in which various nervous symptoms disappeared after the expulsion of 

 a tape-worm. In a case of epilepsy which had persisted for three years Marx 

 saw a cure take place after the expulsion of tenia solium. In a patient who 

 suffered from tabetic phenomena, and in whom there was marked temporary 

 myosis and loss of the pupillary reaction, Denti noted that all symptoms were 

 cured by the expulsion of a tenia solium. Noticeable, too, are the frequent 

 reports of disturbances of the visual apparatus in helminthiasis. In short, it 

 is certain that considerable disturbance of health, sometimes even serious dan- 

 ger to life, may be caused by the presence of parasites. 



It is obvious that delicate, nervous, anemic persons suffer much more from 

 the presence of parasites than robust individuals, whose power of resistance is 

 greater, and that the reaction in the former is much more violent. The with- 

 drawal of food-stuffs which are easily assimilated but which often cause the ex- 

 pulsion of the tape-worm chains, meters in length, or numerous ascarides from 

 the intestinal canal, must inevitably, apart from the local reaction, be fol- 

 lowed by injurious sequels, especially in weak persons and children. The 

 presence of hundreds, even thousands, of blood-sucking ankylostomata cannot 

 fail to produce serious disturbances. Parasites which have lodged in vital 

 organs, in the liver, lungs, heart and in the eyes, in the brain and the spinal 

 cord, even if relatively small, will certainly cause serious functional disturb- 

 ances and disease. 



The investigations in the last decade by Reyher, Runeberg, Dehio, Scha- 

 piro, Schaumann, and others, have demonstrated that the , animal parasites, 

 especially the bothriocephali, produce toxins which, taken into the blood, may 

 lead to the severe manifestations of pernicious anemia. The secretion of toxic 

 substances by other animal parasites, such as echinococci, ascaris lumbricoides, 

 ankylostoma duodenale, etc., is also probable. We do not as yet know the toxin 

 itself, but we recognize its deleterious effects. 



The number of parasites occurring in man is very large. Every year fur- 

 nishes reports of the appearance of animal parasites until then unknown. In 

 the following I shall review the fauna of man. It seems most practicable to 

 discuss them in a systematic order. I begin, therefore, with those organ- 

 isms which can only with difficulty be separated from the lowest vegetable 

 organisms. 



