348 ENTOZOA. 



whilst the intestinal canal contained numerous sexually mature 

 worms, whose direct genetic relationship with these larvse has 

 since been fully and unequiyocaUy established. 



As I have elsewhere remarked, the genesis and migrations of 

 Trichina are astonishingly rapid, and so far as my knowledge 

 extends, without parallel in this or any other class of parasites ; 

 and this circumstance, in association with the rapid migration of 

 the numerous progeny, bears a strict relation to the rapidity with 

 which the disease runs through its course. The severity of the 

 symptoms will also, in the main, depend upon the number of the 

 migrating larv^ in the bearer ; but there can be no doubt that 

 some persons will suffer less than others, even though they may 

 have swallowed an equal number of Trichinge. As we have seen 

 also, from the statistical facts above quoted, the prevalence of the 

 Trichina helminthiasis, whether confined to a single family, the 

 community of a particular town, or the population of a large 

 district, bears a strict relation to the quantity of trichinous meat 

 eaten by the aforesaid people. Doubtless there are many unre- 

 corded cases in which so few Trichina have been swallowed that 

 the amount of traumatic irritation, produced by their correspondingly 

 small progeny, has been insufficient to excite any particular atten- 

 tion on the part of the unconscious bearer. Supposing even a 

 dozen impregnated female worms gained access to the intestinal 

 canal, each of these producing on an average 150 embryos or 

 thereabouts, the total larval progeny, numbering less than 2000, 

 would probably be incapable of making their presence known or 

 felt within the person of their bearer. 



The experiments of Virchow, Leuckart, and Davaine, all tend 

 to show that the effects produced on animals by the Trichina are 

 very similar to those occasioned in man. All three of these savans 

 have minutely recorded these phenomena. As they have, however, 

 been described and summarized by the last-named author in a 

 memoir recently communicated to the Biological Society of Paris, 

 I shall close this chapter by a quotation from the paper in ques- 



