44 



THE AMEKICAN MONTHLY 



[March, 



such flesh by way of experiment. 

 Nevertheless one often finds parasites 

 still enclosed in their capsules on the 

 third day after feeding such flesh to 

 an animal. There is scarcely another 

 worm in which the matured stage is 

 reached in so brief a period. Under 

 these circumstances it must be evi- 

 dent that the changes necessary to 

 maturity for these parasites are not 

 very great. As a rule, sexual connec- 

 tion takes place within two days from 

 the time the trichina become free. 

 The parasites increase in length and 

 thickness, and, in the female, the 

 uterus fills with fructified ova, which 

 soon develop into embryos enclosed 

 in the body of the female. Leuckart 

 states that the female intestinal, or 

 ^matured parasite lives from five to 

 i six weeks, and produces at least fif- 

 ' teen hundred embryos. In the intes- 

 tines of the animal invaded, the fe- 

 males greatly predominate over the 

 male parasites. The newly-born em- 

 bryos are at first buried in the mucus 

 which lines the intestinal tract, as 

 free and movable parasites. They 

 soon, however, begin their migration 

 and dispersion, the first act being 

 the penetration of the intestinal walls. 

 It seems still to be a matter of dis- 

 cussion, as to the means or ways by 

 which further migration takes place. 

 Some authorities, and among them 

 the most eminent, as Leuckart, 

 Furstenburg, and Gerlach, favor the 

 view that the parasites proceed by 

 way of the mesenterium and con- 

 nective-tissue tracts over the system, 

 and penetrate the sarcolemma, or 

 connective-tissue membrane of the 

 muscular fibres, to lodge in the sub- 

 stance of the same. Here the para- 

 site develops a capsule or bed of 

 finely granulous character for itself, 

 the sarcous elements of the fibres of 

 the muscles becoming wasted, or 

 used up, and their striation lost so 

 far as the capsule of the parasite 

 extends. The sarcolemma of the 

 muscle fibres forms a thickened 

 secondary capsule around the para- 

 site. 



Another view, the possibility of 

 which is conceded in a minor degree 

 by the above-named authorities, is 

 that the parasites gain access to the 

 circulation, and are transported over 

 the system by the moving fluid, bor- 

 ing through the smaller vessels at 

 convenience, and by this means gain- 

 ing access to the muscular tissues. 



Thus it is evident that the con- 

 sumer of trichinous flesh provides 

 the means for its own infection. 

 While this is in general the manner 

 by which infection takes place, it by 

 no means excludes the possibility of 

 the infection of an animal by intesti- 

 nal trichina which have passed from 

 an already infected organism with 



Fig. 12. — Encapsuled concretions with dead 

 Trichinae. (Leuckart). 



its faeces. In this way an infected 

 swine may infect others, or in fact 

 give occasion to a secondary infec- 

 tion of itself, by rooting in the man- 

 ure of its pen. In the same way swine 

 may become infected from infected 

 men when, as is too often the case, 

 the out-houses for the family are 

 placed over the piggery, or lead 

 into it, or where the contents of the 

 same are thrown into the piggery for 

 the swine to work over. Thus we 

 see the cycle of infection may fre- 

 quently continue from swine to man, 

 and from man to swine. 



[It appears, from a table which ac- 



