ZOOLOGY AND MEDICINE. 447 



eiiornious advances have been made during the past twenty-five 

 years! How nianj^ species of parasites have been added to the list 

 which Avas then so restricted ! The complete study of these animals 

 necessitates very technical zoological knowledge; it is not sufficient 

 to determine their structure, to follow their migrations and metamor- 

 phoses, to recognize them in their different transformations. To ascer- 

 tain the lesions which they j^roduce Ave must also knoAv the parasites 

 of the most A^arious kinds of animals in order to discover the rela- 

 tionship that may exist betAveen those that inhabit man and those 

 found in different species. 



Davaine described, from A^ery imperfect specimens, a little taenia 

 coming from the Comorin Islands, to Avhich he gaA^e the name Tamia 

 niadagascaroisis. Cobbold published, under the name of Dhtoma 

 rbujer'u a trematocle that lives in Japan and China in the lungs of 

 man and A\'liich frequently causes haemoptysis. Who, then, without 

 possessing the knoAvledge I have just mentioned and Avhich can only 

 be acquired by long practice in zoologA^, Avould haA^e suspected that the 

 first of these parasites belongs to a tj^pe found only quite exception- 

 ally in mammals and man, but Avhich normally belongs to the 

 Gallinacea^? Who, then, except under such circumstances, Avould 

 have recognized in the second one a parasite already discovered by 

 Kerbert in the tiger? Such relations are not merely simple curiosi- 

 ties, as superficial minds might suppose; they are of the highest 

 importance, since they put us on the track of the origin of the 

 parasitic diseases of man, the only ones on the whole that are inter- 

 esting to the physician. It would be easy to cite other examples 

 illustrating this proposition in an equally clear manner. 



From a more strictly medical point of view the Helminthes, or 

 intestinal Avorms, are about to resume in medicine the part which 

 Avas in former times attributed to them without contest, but Avhich 

 Avas taken from them by the progress of bacteriolog}\ The discoA^ery 

 of the pathogenic role of microbes caused a surprising progress in the 

 etiology, prophylaxis, and treatment of infectious diseases. By a 

 very comprehensible exaggeration CA^erything was ascribed to bacteria, 

 and it Avas a great comfort to medicine to find in them an explanation 

 of phenomena that had for centuries obstinately refused to give up 

 their secret. It is far from being my intention to contest the impor- 

 tant part which bacteria play in the production of disease, but I am 

 clearly of the opinion that often they are injurious only because they 

 have been preceded in their pernicious Avork by A^arious Helminthes 

 which have prepared the Ava}^ for them and enabled them to produce 

 their deleterious effects. 



Guiart found that the Ascarls conocephubla produces in the intes- 

 tinal mucous membrane of the dolphin quite deep erosions, due to 

 the three powerful nodules with Avhich its mouth is armed; the 



