IN THE BODIES OF ANIMALS. 399 



insurmountable objections, which I should like briefly to notice 

 in this place. 



If it be true that mothers communicate worms to their 

 foetuses, they must nourish in their own bodies all the species 

 of worms communicable. Let us see if this is probable. 



There are twelve species of worms, if not more, known to 

 infest man. These are — 1. Filaria medh/ensls. 2. Hamularia 

 lymphatica. o. Trichocejihalus. 4. Ascaris lumbricoides. 

 5. Shongylus gigcts. 6. Bothriocephalus. 7. Distoma hepa- 

 iicum. 8. Poly stoma pingidcola. 9. Taenia lata. 10. Tcenia 

 solium. \\. Cysticercus. 12. Ec/iinococcus. We find in the 

 horse nine distinct w^orms ; namely — I. Filaria. 2. Odyitris. 

 3. Ascaris. 4. .Stro7igylus gigas. 5. S. artnatus. 6. Dis- 

 toma. 7. Tcenia perfoUata. 8. T. jilicata. 9. Cysticercus. 

 In Colymbus Septentrionalis there are seven: Strongylus ; 

 two species of Ascaris ; Distoma ; Amphistoma ; two species 

 of Bothriocephalus. In Rana temporaria as many : two 

 species of Ascaris ; Strongylus ; Echinorhynchus ; Distoma ; 

 Amphistoma ; Polystoma. A similar number infest Gas- 

 terosteus aculeatus : Ascaris ; Echinorhynchus ; Monostoma ; 

 Distoma ; Tricuspidaria ; Bothriocephalus ; and Tcenia. 

 It is needless to cite more examples. Now it has never 

 occurred to any one to find in one subject all the species of 

 worms peculiar to a certain animal. No woman was ever 

 infested with the twelve species of worms above enumerated, 

 and no individual mare ever contained the nine species of worms 

 which have been found in the horse ; and so of the rest. Some 

 species of worms are exceedingly rare. The Cysticercus, for 

 instance, is by no means frequently found in man or in the 

 horse ; indeed, some had doubted its existence altogether in 

 the horse, till it was found by Chabertus. It is characterised 

 by a long attenuated caudal vesicle. The Echinococcus is 

 observed but rarely in man ; it may be found, perhaps, in one 

 or two instances in many thousands. The Tcenia themselves, 

 one species at least, are rare in certain situations ; the T. lata 

 is rarely found with us. 



Now if, after a lapse of ten generations, or more, a very rare 

 species of worm should be found in a descendant of this stock, we 

 must conceive the eggs to have been transmitted by all the female 

 parents, and to have been eventually deposited in this solitary 

 individual, which, in my opinion, is to conceive an absurdity. 



